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    Antihistamine and Opioid Antitussive Combinations

    BOXED WARNING

    Alcoholism, depression, substance abuse

    Codeine is an opioid agonist and therefore has abuse potential and a risk for fatal overdose from depressed respiration. Consumption of codeine with ethanol will result in additive central nervous system (CNS) and respiratory depressant effects. Patients with alcoholism should be advised of this serious risk, or an alternative medication should be used. Addiction may occur in patients who obtain codeine illicitly or in those appropriately prescribed the drug. The risk of addiction in any individual is unknown. Patients with an individual or family history of substance abuse (including alcoholism) or mental illness (e.g., major depression) have an increased risk of opioid abuse. Assess patients for risks of addiction, abuse, or misuse before drug initiation, and monitor patients who receive opioids routinely for development of these behaviors or conditions. Abuse and addiction are separate and distinct from physical dependence and tolerance; patients with addiction may not exhibit tolerance and symptoms of physical dependence. To discourage abuse, reserve chlorpheniramine; codeine for use in adult patients for whom the benefits of cough suppression are expected to outweigh the risks, and in whom an adequate assessment of the etiology of the cough has been made. Prescribe the smallest appropriate quantity for the shortest duration that is consistent with individual treatment goals. Proper disposal instructions for unused drug should be given to patients; refill only after reevaluation of the need for continued treatment.

    Asthma, chronic obstructive pulmonary disease (COPD), coadministration with other CNS depressants, coma, cor pulmonale, hypoxemia, neuromuscular disease, obesity, pulmonary disease, respiratory depression, respiratory insufficiency, scoliosis, sleep apnea, status asthmaticus

    Chlorpheniramine; codeine is contraindicated for use in patients with significant respiratory depression and in patients with acute or severe asthma (e.g., status asthmaticus) in unmonitored care settings or in the absence of resuscitative equipment. Receipt of moderate codeine doses in these patients may significantly decrease pulmonary ventilation. Additionally, avoid coadministration with other CNS depressants when possible, as this significantly increases the risk for profound sedation, respiratory depression, coma, and death. Opioid analgesics and antitussives, including codeine, should not be used in patients with acute febrile illness associated with productive cough or in patients with chronic respiratory disease where interference with ability to clear the tracheobronchial tree of secretions would have a deleterious effect on the patient's respiratory function. In patients with chronic obstructive pulmonary disease (COPD), cor pulmonale, decreased respiratory reserve, hypoxia, hypercapnia, respiratory insufficiency, upper airway obstruction, neuromuscular disease, or preexisting respiratory depression, it is recommended that non-opioid antitussives be considered as alternatives to codeine, as even usual therapeutic doses of codeine may decrease respiratory drive and cause apnea in these patient populations. Extreme caution should also be used in patients with chronic asthma, kyphoscoliosis (a type of scoliosis), hypoxemia, or paralysis of the phrenic nerve. Patients with advanced age, debilitation, or sleep apnea are at an increased risk for the development of respiratory depression associated with codeine. Use with caution in patients with obesity as this is a risk factor for obstructive sleep-apnea syndrome and/or decreased respiratory reserve. Respiratory depression, if left untreated, may cause respiratory arrest and death. Symptoms of respiratory depression include a reduced urge to breathe, a decreased respiratory rate, or deep breaths separated by long pauses (a "sighing" breathing pattern). Carbon dioxide (CO2) retention from respiratory depression may also worsen opioid sedating effects. Concomitant use of chlorpheniramine; codeine with CYP3A4 inhibitors or inducers, or CYP2D6 inhibitors should be avoided whenever possible. Use of a CYP3A4 inhibitor may result in an increase in codeine plasma concentrations with subsequently greater metabolism by CYP2D6, resulting in greater morphine levels, which could increase or prolong adverse reactions and may cause potentially fatal respiratory depression, particularly when an inhibitor is added after a stable dose of the codeine-containing antitussive is achieved. After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, it may result in lower codeine levels, greater norcodeine levels, and less metabolism via CYP2D6 with resultant lower morphine levels that may decrease opioid efficacy or cause a withdrawal syndrome in patients who had developed physical dependence to codeine. The concomitant use of a CYP3A4 inducer can result in lower codeine levels, greater norcodeine levels, and less metabolism via CYP2D6 with resultant lower morphine levels, resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of active metabolite morphine, which could result in reduced efficacy. After stopping a CYP2D6 inhibitor, as the effects of the inhibitor decline, the codeine plasma concentration will decrease but the active metabolite morphine plasma concentration will increase, which could result in potentially fatal respiratory depression. To reduce the risk of respiratory depression, proper dosing of chlorpheniramine; codeine is essential. Monitor patients closely, especially within the first 24 to 72 hours of initiating therapy or when used in patients at higher risk. An unresponsive cough should be reevaluated in 5 days or sooner for possible underlying pathology, such as foreign body or lower respiratory tract disease. Management of respiratory depression should include observation, necessary supportive measures, and opioid antagonist use when indicated.

    Accidental exposure, ethanol ingestion, ethanol intoxication, potential for overdose or poisoning

    Like all opioid agonists, codeine is associated with a significant potential for overdose or poisoning; proper patient selection and counseling is recommended. Ensure accuracy when prescribing, dispensing, and administering chlorpheniramine; codeine cough products as dosing errors can result in accidental overdose and death. Chlorpheniramine; codeine should be kept out of the reach of pediatric patients, others for whom the drug was not prescribed, and pets, as accidental exposure of even 1 dose of codeine may cause respiratory failure and a fatal overdose. Ethanol ingestion with chlorpheniramine; codeine products will result in additive CNS depressant effects which may lead to respiratory depression; ethanol intoxication must be avoided. Advise patients to avoid alcohol ingestion, including the ingestion of alcohol contained in prescription or non-prescription medications, during therapy.

    Labor, neonatal opioid withdrawal syndrome, obstetric delivery, pregnancy

    There are no adequate studies of chlorpheniramine; codeine in pregnant women; avoid use during pregnancy. Both codeine and chlorpheniramine cross the placenta. There is an increased neonatal risk if codeine is used near term. Doses administered close to obstetric delivery may increase the risk for respiratory depression in the newborn. Codeine should be avoided during labor if obstetric delivery of a premature neonate is expected. Neonatal respiratory depression may occur at birth or within a few days. Further, prolonged use of opioids such as codeine during pregnancy may cause neonatal opioid withdrawal syndrome (NOWS) in the newborn. This syndrome can be life-threatening. Severe symptoms may require pharmacologic therapy managed by clinicians familiar with neonatal opioid withdrawal. Monitor the newborn for withdrawal symptoms including irritability, hyperactivity, abnormal sleep pattern, high-pitched crying, tremor, vomiting, diarrhea, and failure to gain weight. Onset, duration, and severity of opioid withdrawal may vary based on the specific opioid used, duration of use, timing and amount of last maternal use, and rate of elimination by the newborn. Published data from case-control and observational studies on codeine use during human pregnancy with respect to congenital issues are inconsistent in their findings. Some studies of codeine exposure showed an increased risk of overall congenital malformations while others did not; the studies suffer from small sample sizes and quality of the evidence/studies. The majority of studies examining the use of chlorpheniramine in human pregnancy did not find an association with an increased risk of congenital anomalies. In the few studies reporting an association, there was no consistent pattern of malformations noted.

    DEA CLASS

    Rx, schedule III

    DESCRIPTION

    Oral sedating antihistamine and opiate agonist antitussive combination
    Used in adults for temporary relief from cough and other symptoms due to hay fever, upper respiratory allergies, or allergic rhinitis
    Safety and efficacy not established in pediatric patients under 18 years of age; contraindicated for cough and cold in all pediatric patients less than 12 years of age and in adolescent pediatric patients 12 to 18 years after tonsillectomy or adenoidectomy

    COMMON BRAND NAMES

    Tuxarin ER, Tuzistra XR

    HOW SUPPLIED

    Chlorpheniramine Maleate, Codeine Phosphate/Chlorpheniramine, Codeine Phosphate Oral Tab ER: 8-54.3mg
    Chlorpheniramine Polistirex, Codeine Polistirex/Chlorpheniramine, Codeine Polistirex/TUZISTRA XR Oral Susp ER: 5mL, 2.8-14.7mg

    DOSAGE & INDICATIONS

    For the temporary relief of cough and upper respiratory symptoms (e.g., rhinorrhea, sneezing, itching of the nose or throat or itchy, watery eyes) associated with allergy (allergic rhinitis) or the common cold.
    Oral dosage (extended-release oral suspension, e.g., Tuzistra XR,- codeine polistirex/chlorpheniramine polistirex providing 14.7 mg of codeine with 2.8 mg of chlorpheniramine per 5 mL)
    Adults

    10 mL PO every 12 hours. Max: Do not exceed 20 mL total in 24 hours. Lower doses may be more appropriate for geriatric or debilitated patients, dependent upon renal and hepatic function, and/or concomitant medications. LIMITATION OF USE: Reserve chlorpheniramine; codeine for use in adult patients for whom the benefits of cough suppression are expected to outweigh the risks, and in whom an adequate assessment of the etiology of the cough has been made. Prescribe for the shortest duration consistent with individual patient treatment goals. Monitor patients closely for respiratory depression, especially within the first 24 to 72 hours of initiating therapy; proper dosing is essential to reduce the risk of respiratory depression. Reevaluate patients with unresponsive cough in 5 days or sooner for possible underlying pathology, such as foreign body or lower respiratory tract disease. CONTINUED TREATMENT: If a patient requires a refill, reevaluate the cause of the cough and the need for continued treatment within 5 days. DISCONTINUATION: Do not abruptly discontinue this product in a physically-dependent patient; taper the dose gradually, by 25% to 50% every 2 to 4 days, while monitoring carefully for signs and symptoms of withdrawal. If withdrawal occurs, raise the dose to the previous level and taper more slowly, either by increasing the interval between decreases, decreasing the amount of change in dose, or both.

    Oral dosage (extended-release tablets of codeine phosphate and chlorpheniramine maleate, e.g., Tuxarin ER)
    Adults

    1 extended-release (ER) tablet PO every 12 hours. Each ER tablet contains 54.3 mg of codeine phosphate (equivalent to 40 mg of codeine) with 8 mg of chlorpheniramine maleate (equivalent to 5.6 mg of chlorpheniramine). Max: Do not exceed 2 tablets per 24 hours. Lower doses may be more appropriate for geriatric or debilitated patients, dependent upon renal and hepatic function, and/or concomitant medications. LIMITATION OF USE: Reserve for adult patients for whom the benefits of cough suppression are expected to outweigh the risks, and in whom an adequate assessment of the etiology of the cough has been made. Prescribe for the shortest duration consistent with individual patient treatment goals. Monitor patients closely for respiratory depression, especially within the first 24 to 72 hours of initiating therapy; proper dosing is essential to reduce the risk of respiratory depression. Reevaluate unresponsive cough in 5 days or sooner for possible underlying pathology, such as foreign body or lower respiratory tract disease. CONTINUED TREATMENT: If a patient requires a refill, reevaluate the cause of the cough and the need for continued treatment within 5 days. DISCONTINUATION: Do not abruptly discontinue this product in a physically-dependent patient; taper the dose gradually, by 25% to 50% every 2 to 4 days, while monitoring carefully for signs and symptoms of withdrawal. If withdrawal occurs, raise the dose to the previous level and taper more slowly, either by increasing the interval between decreases, decreasing the amount of change in dose, or both.

    MAXIMUM DOSAGE

    Adults

    20 mL/day PO of extended-release (ER) oral suspension or 2 tablets/day PO of ER tablets.

    Geriatric

    20 mL/day PO of extended-release (ER) oral suspension or 2 tablets/day PO of ER tablets.

    Adolescents

    Safety and efficacy have not been established.

    Children

    12 years: Safety and efficacy have not been established.
    Less than 12 years: Use is contraindicated.

    Infants

    Use is contraindicated.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Specific dose adjustment recommendations are not available; decreased elimination of both drugs is expected. Use with caution in patients with severe hepatic impairment, and monitor closely for signs of codeine toxicity (respiratory depression, sedation, and hypotension) and chlorpheniramine toxicity.

    Renal Impairment

    Specific dose adjustment recommendations are not available; however, decreased elimination of both drugs is expected. Use with caution in patients with moderate to severe renal impairment, and monitor closely for signs of codeine toxicity (respiratory depression, sedation, and hypotension) and chlorpheniramine toxicity.

    ADMINISTRATION

     

    Oral Administration

    Administer orally with a full glass of water. May be taken with food or milk to minimize GI irritation.
    Do not administer more frequently than directed as severe, possibly fatal, respiratory depression may occur. An unresponsive cough should be reevaluated in 5 days or sooner for possible underlying pathology, such as foreign body or lower respiratory tract disease.

    Oral Solid Formulations

    Extended-release tablets:
    Swallow whole. Do not cut, crush or chew.

    Oral Liquid Formulations

    Extended-release oral suspension (e.g., Tuzistra XR suspension)
    Shake the suspension well before each use.
    Advise patients/caregivers to use a calibrated spoon or other measuring device. Do not to overfill.
    Rinse the measuring device with water after each use.

    STORAGE

    Generic:
    - Protect from light
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    Cotab AX :
    - Protect from light
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    EndaCof-C:
    - Store at room temperature (between 59 to 86 degrees F)
    Notuss-AC:
    - Store at room temperature (between 59 to 86 degrees F)
    TL-HIST CM:
    - Store at room temperature (between 59 to 86 degrees F)
    Tuxarin ER:
    - Store at controlled room temperature (between 68 and 77 degrees F)
    Tuzistra XR:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    Zodryl AC:
    - Protect from light
    - Store at room temperature (up to 77 degrees F)
    Zodryl AC Adult:
    - Store at room temperature (up to 77 degrees F)
    Z-Tuss AC:
    - Store at room temperature (between 59 to 86 degrees F)

    CONTRAINDICATIONS / PRECAUTIONS

    Opiate agonist hypersensitivity

    The use of chlorpheniramine; codeine is contraindicated in patients who have hypersensitivity to codeine, chlorpheniramine, or any of the inactive ingredients in the product. Although true opiate agonist hypersensitivity is rare, patients who have demonstrated a prior codeine hypersensitivity reaction should not receive codeine or other opioid agonists of the phenanthrene subclass including morphine, oxycodone, and hydromorphone.

    Alcoholism, depression, substance abuse

    Codeine is an opioid agonist and therefore has abuse potential and a risk for fatal overdose from depressed respiration. Consumption of codeine with ethanol will result in additive central nervous system (CNS) and respiratory depressant effects. Patients with alcoholism should be advised of this serious risk, or an alternative medication should be used. Addiction may occur in patients who obtain codeine illicitly or in those appropriately prescribed the drug. The risk of addiction in any individual is unknown. Patients with an individual or family history of substance abuse (including alcoholism) or mental illness (e.g., major depression) have an increased risk of opioid abuse. Assess patients for risks of addiction, abuse, or misuse before drug initiation, and monitor patients who receive opioids routinely for development of these behaviors or conditions. Abuse and addiction are separate and distinct from physical dependence and tolerance; patients with addiction may not exhibit tolerance and symptoms of physical dependence. To discourage abuse, reserve chlorpheniramine; codeine for use in adult patients for whom the benefits of cough suppression are expected to outweigh the risks, and in whom an adequate assessment of the etiology of the cough has been made. Prescribe the smallest appropriate quantity for the shortest duration that is consistent with individual treatment goals. Proper disposal instructions for unused drug should be given to patients; refill only after reevaluation of the need for continued treatment.

    Asthma, chronic obstructive pulmonary disease (COPD), coadministration with other CNS depressants, coma, cor pulmonale, hypoxemia, neuromuscular disease, obesity, pulmonary disease, respiratory depression, respiratory insufficiency, scoliosis, sleep apnea, status asthmaticus

    Chlorpheniramine; codeine is contraindicated for use in patients with significant respiratory depression and in patients with acute or severe asthma (e.g., status asthmaticus) in unmonitored care settings or in the absence of resuscitative equipment. Receipt of moderate codeine doses in these patients may significantly decrease pulmonary ventilation. Additionally, avoid coadministration with other CNS depressants when possible, as this significantly increases the risk for profound sedation, respiratory depression, coma, and death. Opioid analgesics and antitussives, including codeine, should not be used in patients with acute febrile illness associated with productive cough or in patients with chronic respiratory disease where interference with ability to clear the tracheobronchial tree of secretions would have a deleterious effect on the patient's respiratory function. In patients with chronic obstructive pulmonary disease (COPD), cor pulmonale, decreased respiratory reserve, hypoxia, hypercapnia, respiratory insufficiency, upper airway obstruction, neuromuscular disease, or preexisting respiratory depression, it is recommended that non-opioid antitussives be considered as alternatives to codeine, as even usual therapeutic doses of codeine may decrease respiratory drive and cause apnea in these patient populations. Extreme caution should also be used in patients with chronic asthma, kyphoscoliosis (a type of scoliosis), hypoxemia, or paralysis of the phrenic nerve. Patients with advanced age, debilitation, or sleep apnea are at an increased risk for the development of respiratory depression associated with codeine. Use with caution in patients with obesity as this is a risk factor for obstructive sleep-apnea syndrome and/or decreased respiratory reserve. Respiratory depression, if left untreated, may cause respiratory arrest and death. Symptoms of respiratory depression include a reduced urge to breathe, a decreased respiratory rate, or deep breaths separated by long pauses (a "sighing" breathing pattern). Carbon dioxide (CO2) retention from respiratory depression may also worsen opioid sedating effects. Concomitant use of chlorpheniramine; codeine with CYP3A4 inhibitors or inducers, or CYP2D6 inhibitors should be avoided whenever possible. Use of a CYP3A4 inhibitor may result in an increase in codeine plasma concentrations with subsequently greater metabolism by CYP2D6, resulting in greater morphine levels, which could increase or prolong adverse reactions and may cause potentially fatal respiratory depression, particularly when an inhibitor is added after a stable dose of the codeine-containing antitussive is achieved. After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, it may result in lower codeine levels, greater norcodeine levels, and less metabolism via CYP2D6 with resultant lower morphine levels that may decrease opioid efficacy or cause a withdrawal syndrome in patients who had developed physical dependence to codeine. The concomitant use of a CYP3A4 inducer can result in lower codeine levels, greater norcodeine levels, and less metabolism via CYP2D6 with resultant lower morphine levels, resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of active metabolite morphine, which could result in reduced efficacy. After stopping a CYP2D6 inhibitor, as the effects of the inhibitor decline, the codeine plasma concentration will decrease but the active metabolite morphine plasma concentration will increase, which could result in potentially fatal respiratory depression. To reduce the risk of respiratory depression, proper dosing of chlorpheniramine; codeine is essential. Monitor patients closely, especially within the first 24 to 72 hours of initiating therapy or when used in patients at higher risk. An unresponsive cough should be reevaluated in 5 days or sooner for possible underlying pathology, such as foreign body or lower respiratory tract disease. Management of respiratory depression should include observation, necessary supportive measures, and opioid antagonist use when indicated.

    Brain tumor, head trauma, increased intracranial pressure

    Avoid the use of chlorpheniramine; codeine in patients with head trauma, intracranial lesions, or pre-existing increased intracranial pressure. In patients who may be susceptible to the intracranial effects of carbon dioxide (CO2) retention (e.g., those with evidence of increased intracranial pressure or brain tumor), chlorpheniramine; codeine may reduce respiratory drive, and the resultant CO2 retention can further increase intracranial pressure. Furthermore, opioids produce adverse reactions that may obscure the clinical course of patients with head injuries.

    Asian patients, Black patients, Hispanic patients, poor metabolizers, White patients

    When prescribing chlorpheniramine; codeine, consider the race-related prevalence of altered codeine metabolism, including that of Asian patients, Black patients, White patients, Hispanic patients, and Middle Eastern patients. Some individuals may be ultra-rapid metabolizers due to a specific CYP2D6 genotype (gene duplications noted as *1/*1xN or *1/*2xN). People who are ultra-rapid metabolizers should not use codeine-containing products. Ultra-rapid metabolizers convert codeine into morphine more rapidly and completely than other people. Higher than expected serum morphine concentrations occur due to the rapid conversion and serious toxicity, including life-threatening or fatal respiratory depression, may occur. The prevalence of this CYP2D6 phenotype varies widely and has been estimated at 1% to 10% in White patients, 3% to 4% in Black patients (African Americans), 1% to 2% in East Asian patients (Chinese, Japanese, Korean), and may be greater than 10% in certain racial/ethnic groups (e.g., Oceanian, Northern African, Middle Eastern, Ashkenazi Jews, Puerto Rican). In contrast, patients who are poor metabolizers of CYP2D6 may not adequately convert codeine to morphine and may not experience the expected therapeutic response to codeine. The contribution of active metabolites to the overall antitussive effect of codeine is not known but should be considered. Approximately 7% to 10% of the White patient population lacks functional CYP2D6 activity.

    Accidental exposure, ethanol ingestion, ethanol intoxication, potential for overdose or poisoning

    Like all opioid agonists, codeine is associated with a significant potential for overdose or poisoning; proper patient selection and counseling is recommended. Ensure accuracy when prescribing, dispensing, and administering chlorpheniramine; codeine cough products as dosing errors can result in accidental overdose and death. Chlorpheniramine; codeine should be kept out of the reach of pediatric patients, others for whom the drug was not prescribed, and pets, as accidental exposure of even 1 dose of codeine may cause respiratory failure and a fatal overdose. Ethanol ingestion with chlorpheniramine; codeine products will result in additive CNS depressant effects which may lead to respiratory depression; ethanol intoxication must be avoided. Advise patients to avoid alcohol ingestion, including the ingestion of alcohol contained in prescription or non-prescription medications, during therapy.

    Driving or operating machinery

    Any patient receiving chlorpheniramine; codeine should be warned about the possibility of sedation and to use caution when driving or operating machinery. Codeine may produce marked drowsiness and impair the mental and/or physical abilities required for the performance of potentially hazardous tasks. Chlorpheniramine is a sedating antihistamine that may have additive effects. Advise patients to avoid engaging in hazardous tasks requiring mental alertness and motor coordination after ingestion of chlorpheniramine; codeine. Avoid concurrent use of this cough product with alcohol or other CNS depressants because additional impairment of central nervous system performance may occur.

    Abrupt discontinuation

    Chlorpheniramine; codeine is not intended for prolonged use for cough. Abrupt discontinuation of prolonged codeine therapy can result in withdrawal symptoms. Gradually reduce the dose to prevent signs and symptoms of withdrawal in the physically-dependent patient. Avoid use of partial agonists (e.g., buprenorphine), mixed agonist/antagonists (e.g., nalbuphine), or pure antagonists (e.g., naloxone) in patients physically dependent on opioids, as an acute withdrawal syndrome may precipitate. The severity of the withdrawal syndrome produced will depend on the degree of physical dependence and on the administered dose of the concomitant drug. If treatment of respiratory depression in an individual physically dependent on opioids is necessary, administer the opioid antagonist with extreme care; titrate the antagonist dose by using smaller than usual doses. In addition, the use of partial agonists or mixed agonist/antagonists in patients who have received or are receiving codeine should be avoided as these medications may reduce the therapeutic effect of codeine.

    Cardiac disease, dehydration, hypotension, hypovolemia, orthostatic hypotension, shock, syncope

    Chlorpheniramine; codeine may cause severe hypotension including orthostatic hypotension and syncope in ambulatory patients. There is increased risk in patients whose ability to maintain blood pressure has already been compromised by a reduced blood volume (hypovolemia or dehydration) or concurrent administration of certain CNS depressant drugs (e.g., phenothiazines or general anesthetics). Also use with caution in patients with significant cardiac disease. Monitor these patients for signs of hypotension after initiating chlorpheniramine; codeine. In patients with circulatory shock, codeine may cause vasodilation that can further reduce cardiac output and blood pressure. Avoid the use of chlorpheniramine; codeine in patients with circulatory shock.

    Acute abdomen, constipation, diarrhea, GI disease, GI obstruction, ileus, inflammatory bowel disease, ulcerative colitis

    Chlorpheniramine; codeine is contraindicated in patients with known or suspected GI obstruction, including paralytic ileus. Due to the effects of opiate agonists on the gastrointestinal tract, chlorpheniramine; codeine should be used cautiously in patients with GI disease, such as ulcerative colitis (UC). Patients with UC or other inflammatory bowel disease may be more sensitive to constipation caused by opioid agonists. Opioid agonists may obscure the diagnosis or clinical course in patients with acute abdomen. Although opiate agonists are contraindicated for use in patients with diarrhea secondary to poisoning or infectious diarrhea, antimotility agents have been used successfully in these patients. If possible, opiate agonists should not be given until the toxic substance has been eliminated.

    Biliary tract disease, gallbladder disease, pancreatitis

    Chlorpheniramine; codeine should be used with caution in patients with biliary tract disease, such as acute pancreatitis and gallbladder disease. As with other opioid agonists, codeine may cause spasm of the sphincter of Oddi, increasing biliary tract pressure. Biliary effects due to opiate agonists have resulted in an increase in plasma amylase and lipase concentrations up to 2 to 15 times the normal values; determination of these enzyme levels may be unreliable for 24 hours after administration.

    Hepatic disease

    Chlorpheniramine; codeine should be used with caution in patients with severe hepatic disease, and patients should be monitored closely for respiratory depression, sedation, and hypotension. Patients with severe hepatic impairment may have higher plasma concentrations of codeine or chlorpheniramine than those with normal hepatic function. Patients with severe hepatic disease may experience an increased risk for toxicity. Patients with hepatic disease may require lower doses and/or less frequent dosing intervals. Carefully monitor patients for respiratory depression, sedation, and hypotension.[59535]

    Renal failure, renal impairment

    Chlorpheniramine; codeine should be used with caution in patients with severe renal impairment or renal failure, and these patients should be monitored closely for codeine effects such as respiratory depression, sedation, and hypotension. Both chlorpheniramine and codeine accumulation or prolonged duration of action may occur in patients with severe renal impairment. In acute situations, such patients require close monitoring to avoid excessive toxicity. Patients with chronic renal disease may require lower doses or less frequent dosing intervals.

    Bladder obstruction, prostatic hypertrophy, urethral stricture, urinary retention

    Codeine increases the tension of the detrusor muscle of the bladder, and may increase the risk for urinary retention. Medications with anticholinergic properties, such as chlorpheniramine, can also increase the risk for urinary difficulties in at-risk patients. Patients more prone to urinary tract effects include those patients with prostatic hypertrophy, urethral stricture, bladder obstruction, or pelvic tumors. The concomitant use of other anticholinergic drugs with chlorpheniramine; codeine may increase the risk of urinary retention.

    Closed-angle glaucoma, contact lenses

    Give chlorpheniramine; codeine with caution in patients with closed-angle glaucoma due to the anticholinergic effects of chlorpheniramine. Opiate agonists such as codeine may cause changes in accommodation. Antihistamines such as chlorpheniramine may cause dry eyes that may be of significance in wearers of contact lenses.

    Seizure disorder, seizures

    Codeine may increase the frequency of seizures in patients with a seizure disorder, and may increase the risk of seizures occurring in other clinical settings associated with seizures. Monitor patients with a history of seizure disorders for worsened seizure control during chlorpheniramine; codeine therapy.

    Adrenal insufficiency, hypothyroidism, myxedema

    Use chlorpheniramine; codeine with caution in patients with Addison's disease or other conditions of adrenal insufficiency. Cases of adrenal insufficiency have been reported with opioid use, more often following more than 1 month of use. Presentation of adrenal insufficiency may include non-specific symptoms and signs including nausea, vomiting, anorexia, fatigue, weakness, dizziness, and low blood pressure. If adrenal insufficiency is suspected, confirm the diagnosis with diagnostic testing as soon as possible. If adrenal insufficiency is diagnosed, treat with physiologic replacement doses of corticosteroids. Wean the patient off of the opioid to allow adrenal function to recover and continue corticosteroid treatment until adrenal function recovers. Other opioids may be tried as some cases reported use of a different opioid without recurrence of adrenal insufficiency. The information available does not identify any particular opioids as being more likely to be associated with adrenal insufficiency. Opioids inhibit the secretion of adrenocorticotropic hormone (ACTH), cortisol, and luteinizing hormone (LH). Monitor patients for symptoms of opioid-induced endocrinopathy, particularly those receiving a daily dose equivalent to 100 mg or more of morphine. Patients should seek immediate medical attention if they experience symptoms of adrenocortical insufficiency. Chronic opioid use may lead to symptoms of hypogonadism, resulting from changes in the hypothalamic-pituitary-gonadal axis. Male patients with signs or symptoms of androgen deficiency should undergo evaluation. Patients with hypothyroidism or myxedema should also receive opioid therapy with caution, as thyroid stimulating hormone (TSH) may be either stimulated or inhibited by opioids.

    Labor, neonatal opioid withdrawal syndrome, obstetric delivery, pregnancy

    There are no adequate studies of chlorpheniramine; codeine in pregnant women; avoid use during pregnancy. Both codeine and chlorpheniramine cross the placenta. There is an increased neonatal risk if codeine is used near term. Doses administered close to obstetric delivery may increase the risk for respiratory depression in the newborn. Codeine should be avoided during labor if obstetric delivery of a premature neonate is expected. Neonatal respiratory depression may occur at birth or within a few days. Further, prolonged use of opioids such as codeine during pregnancy may cause neonatal opioid withdrawal syndrome (NOWS) in the newborn. This syndrome can be life-threatening. Severe symptoms may require pharmacologic therapy managed by clinicians familiar with neonatal opioid withdrawal. Monitor the newborn for withdrawal symptoms including irritability, hyperactivity, abnormal sleep pattern, high-pitched crying, tremor, vomiting, diarrhea, and failure to gain weight. Onset, duration, and severity of opioid withdrawal may vary based on the specific opioid used, duration of use, timing and amount of last maternal use, and rate of elimination by the newborn. Published data from case-control and observational studies on codeine use during human pregnancy with respect to congenital issues are inconsistent in their findings. Some studies of codeine exposure showed an increased risk of overall congenital malformations while others did not; the studies suffer from small sample sizes and quality of the evidence/studies. The majority of studies examining the use of chlorpheniramine in human pregnancy did not find an association with an increased risk of congenital anomalies. In the few studies reporting an association, there was no consistent pattern of malformations noted.

    Breast-feeding

    Breast-feeding is not recommended when taking chlorpheniramine; codeine due to the risk of serious adverse reactions including excessive sedation and respiratory depression in the breast-fed infant. If an infant is exposed to codeine through breast milk, they should be monitored for excessive sedation and respiratory depression. Withdrawal symptoms can occur in breast-fed infants when maternal use of an opioid is stopped or when breast-feeding is stopped. There is no information on the effects of codeine on milk production, but both codeine and its active metabolite, morphine, are excreted into human milk. In women with normal codeine metabolism (normal CYP2D6 activity), the amount of codeine secreted into human milk is low and dose-dependent. An infant nursing from an ultra-rapid metabolizer (CYP2D6 rapid metabolizer) woman taking codeine could potentially be exposed to high morphine (metabolite) concentrations and experience life-threatening respiratory depression. At least 1 death has been reported in an infant exposed to high levels of morphine in breast milk because the mother was an ultra-rapid metabolizer. Chlorpheniramine is also excreted in human milk. Although the clinical significance is unknown, the anticholinergic action of chlorpheniramine may suppress lactation or produce side effects in breast-feeding infants such as irritability, disturbed sleeping patterns, drowsiness, hyperexcitability, or excessive crying.

    Adenoidectomy, children, infants, neonates, respiratory infection, tonsillectomy

    Chlorpheniramine; codeine is contraindicated in neonates, infants, and children younger than 12 years and for postoperative pain management in pediatric patients younger than 18 years after a tonsillectomy and/or adenoidectomy. The American Academy of Pediatrics (AAP) recommends against the use of codeine in all pediatric patients for any indication. Avoid use of codeine for analgesia in patients 12 to 18 years of age who have other risk factors for respiratory depression unless the benefits outweigh the risks. Risk factors in pediatric patients include conditions associated with hypoventilation such as postoperative status, obstructive sleep apnea, obesity, respiratory infection, asthma, severe pulmonary disease, neuromuscular disease, and concomitant use of other respiratory depressants. When prescribing codeine for the management of pain in adolescents, choose the lowest effective dose for the shortest period of time and inform patients and caregivers of the risks and the signs of opioid overdose. Codeine metabolism is highly variable and unpredictable, particularly in children younger than 12 years; therapeutic response to recommended doses can range from lack of effect in poor metabolizers to fatality in ultra-rapid metabolizers. Ultra-rapid metabolizers are more likely to convert codeine to morphine quickly, leading to excessive morphine blood concentrations that can result in fatal respiratory depression. Because some children who are normal metabolizers can convert codeine to morphine at rates similar to ultra-metabolizers, this concern extends to all pediatric patients. Chlorpheniramine generally should not be used in neonates and infants due to the possibility of paradoxical CNS stimulation or seizures.

    Geriatric

    Use chlorpheniramine; codeine with caution in geriatric patients or debilitated patients. Geriatric or debilitated patients are more susceptible to adverse reactions from opiate agonists; especially sedation and respiratory depression probably as a result of the altered distribution of the drug and decreased elimination. Initial doses of opiate agonists may need to be reduced, and doses should be carefully titrated taking into account clinical goals, adverse reactions, and concomitant conditions and drugs that may increase CNS depression and depress respiration. Geriatric patients also have an increased susceptibility to anticholinergic effects of chlorpheniramine versus younger adults.[59535] According to the Beers Criteria, first-generation sedating antihistamines are considered potentially inappropriate medications (PIMs) in elderly patients; avoid use as they are highly anticholinergic, there is reduced clearance in advanced age, tolerance develops when used as hypnotics, and there is a greater risk of anticholinergic effects (e.g., confusion, dry mouth, constipation) and toxicity compared to younger adults. Avoid drugs with strong anticholinergic properties in geriatric patients with the following due to the potential for exacerbation of the condition or adverse effects: dementia/cognitive impairment (adverse CNS effects), delirium/high risk of delirium (new-onset or worsening delirium), or lower urinary tract symptoms/benign prostatic hyperplasia in men (urinary retention or hesitancy). Opiate agonists are considered PIMs in geriatric patients with a history of falls or fractures and should be avoided in these populations, except in the setting of severe acute pain, since opiates can produce ataxia, impaired psychomotor function, syncope, and additional falls. If an opiate must be used, consider reducing the use of other CNS-active medications that increase the risk of falls and fractures, and implement other strategies to reduce fall risk.[63923] The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities; cough, cold, and allergy medications should be used only for a limited duration (less than 14 days) unless there is documented evidence of enduring symptoms that cannot otherwise be alleviated. First-generation antihistamines, such as chlorpheniramine, have strong anticholinergic properties and are not considered medications of choice in older individuals.[60742]

    MAOI therapy

    The concurrent use of chlorpheniramine; codeine with monoamine oxidase inhibitors (MAOIs) or within 14 days of MAOI therapy is contraindicated. MAOI interactions with opioids may manifest as serotonin syndrome or opioid toxicity. MAOIs may potentiate the effects of morphine, codeine's active metabolite, including respiratory depression, coma, and confusion.

    ADVERSE REACTIONS

    Severe

    cyanosis / Early / Incidence not known
    respiratory arrest / Rapid / Incidence not known
    increased intracranial pressure / Early / Incidence not known
    pulmonary edema / Early / Incidence not known
    seizures / Delayed / Incidence not known
    ileus / Delayed / Incidence not known
    biliary obstruction / Delayed / Incidence not known
    pancreatitis / Delayed / Incidence not known
    bradycardia / Rapid / Incidence not known
    bronchospasm / Rapid / Incidence not known
    anaphylactoid reactions / Rapid / Incidence not known
    visual impairment / Early / Incidence not known
    ocular hypertension / Delayed / Incidence not known
    neonatal respiratory depression / Rapid / Incidence not known
    neonatal opioid withdrawal syndrome / Delayed / Incidence not known
    aplastic anemia / Delayed / Incidence not known
    agranulocytosis / Delayed / Incidence not known

    Moderate

    constipation / Delayed / 10.0
    psychological dependence / Delayed / 10.0
    physiological dependence / Delayed / 10.0
    respiratory depression / Rapid / Incidence not known
    dyspnea / Early / Incidence not known
    confusion / Early / Incidence not known
    excitability / Early / Incidence not known
    depression / Delayed / Incidence not known
    dyskinesia / Delayed / Incidence not known
    euphoria / Early / Incidence not known
    impaired cognition / Early / Incidence not known
    hyperamylasemia / Delayed / Incidence not known
    palpitations / Early / Incidence not known
    hypotension / Rapid / Incidence not known
    hypertension / Early / Incidence not known
    sinus tachycardia / Rapid / Incidence not known
    orthostatic hypotension / Delayed / Incidence not known
    erythema / Early / Incidence not known
    urinary retention / Early / Incidence not known
    dysuria / Early / Incidence not known
    photophobia / Early / Incidence not known
    blurred vision / Early / Incidence not known
    glycosuria / Early / Incidence not known
    hypoglycemia / Early / Incidence not known
    lactation suppression / Early / Incidence not known
    withdrawal / Early / Incidence not known
    thrombocytopenia / Delayed / Incidence not known

    Mild

    dizziness / Early / 1.0-10.0
    nausea / Early / 1.0-10.0
    drowsiness / Early / 10.0
    xerostomia / Early / 10.0
    restlessness / Early / Incidence not known
    tremor / Early / Incidence not known
    headache / Early / Incidence not known
    insomnia / Early / Incidence not known
    irritability / Delayed / Incidence not known
    agitation / Early / Incidence not known
    anorexia / Delayed / Incidence not known
    vomiting / Early / Incidence not known
    diarrhea / Early / Incidence not known
    gastroesophageal reflux / Delayed / Incidence not known
    dyspepsia / Early / Incidence not known
    abdominal pain / Early / Incidence not known
    syncope / Early / Incidence not known
    rash / Early / Incidence not known
    urticaria / Rapid / Incidence not known
    flushing / Rapid / Incidence not known
    pruritus / Rapid / Incidence not known
    asthenia / Delayed / Incidence not known
    fever / Early / Incidence not known
    weakness / Early / Incidence not known
    increased urinary frequency / Early / Incidence not known
    miosis / Early / Incidence not known
    xerophthalmia / Early / Incidence not known
    mydriasis / Early / Incidence not known
    lacrimation / Early / Incidence not known
    tinnitus / Delayed / Incidence not known
    vertigo / Early / Incidence not known
    menstrual irregularity / Delayed / Incidence not known
    appetite stimulation / Delayed / Incidence not known
    libido increase / Delayed / Incidence not known
    gynecomastia / Delayed / Incidence not known

    DRUG INTERACTIONS

    Abiraterone: (Moderate) Concomitant use of codeine with abiraterone may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of abiraterone could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If abiraterone is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Abiraterone is a moderate inhibitor of CYP2D6.
    Acetaminophen; Caffeine; Dihydrocodeine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Chlorpheniramine; Dextromethorphan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Codeine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Dextromethorphan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Dextromethorphan; Doxylamine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. (Moderate) Concomitant use of opioid agonists with doxylamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with doxylamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Dextromethorphan; Guaifenesin; Pseudoephedrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Dextromethorphan; Phenylephrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Dextromethorphan; Pseudoephedrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Acetaminophen; Dichloralphenazone; Isometheptene: (Moderate) Additive CNS depression may occur if dichloralphenazone is used concomitantly with any of the sedating H1 blockers. Use caution with this combination. Dosage reduction of one or both agents may be necessary.
    Acetaminophen; Diphenhydramine: (Moderate) Concomitant use of opioid agonists with diphenhydramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with diphenhydramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Oxycodone: (Major) Concomitant use of oxycodone with other opiate agonists may lead to additive respiratory and/or CNS depression. Hypotension, profound sedation, coma, respiratory depression, or death may occur. Prior to concurrent use of oxycodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. If a CNS depressant is used concurrently with oxycodone, a reduced dosage of oxycodone and/or the CNS depressant is recommended; use an initial dose of oxycodone at 1/3 to 1/2 the usual dosage. Monitor for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Pamabrom; Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acetaminophen; Pentazocine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity. Coadministration of pentazocine with sedating H1-blockers may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation.
    Acetaminophen; Propoxyphene: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Acrivastine; Pseudoephedrine: (Major) Avoid coadministration of opioid agonists with acrivastine due to the risk of additive CNS depression.
    Aldesleukin, IL-2: (Moderate) Aldesleukin, IL-2 may affect CNS function significantly. Therefore, psychotropic pharmacodynamic interactions could occur following concomitant administration of drugs with significant CNS or psychotropic activity such as opiate agonists. In addition, aldesleukin, IL-2, is a CYP3A4 inhibitor and may increase oxycodone plasma concentrations and related toxicities including potentially fatal respiratory depression. If therapy with both agents is necessary, monitor patients for an extended period and adjust oxycodone dosage as necessary.
    Alfentanil: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Aliskiren; Amlodipine: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Aliskiren; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations. (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Aliskiren; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Almotriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Alosetron: (Major) Patients taking medications that decrease GI motility may be at greater risk for serious complications from alosetron, like constipation, via a pharmacodynamic interaction. Constipation is the most frequently reported adverse effect with alosetron. Alosetron, if used with drugs such as opiate agonists, may seriously worsen constipation, leading to events such as GI obstruction/impaction or paralytic ileus. (Moderate) Alosetron, if combined with drugs that possess anticholinergic properties like sedating H1 blockers, may seriously worsen constipation, leading to events such as GI obstruction/impaction or paralytic ileus.
    Alprazolam: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If an opiate agonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the opiate and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Avoid prescribing opiate cough medications in patients taking benzodiazepines.
    Alvimopan: (Moderate) Patients should not take alvimopan if they have received therapeutic doses of opiate agonists for more than seven consecutive days immediately before initiation of alvimopan therapy. Patients recently exposed to opioids are expected to be more sensitive to the effects of mu-opioid receptor antagonists and may experience adverse effects localized to the gastrointestinal tract such as abdominal pain, nausea, vomiting, and diarrhea.
    Amantadine: (Moderate) Medications with significant anticholinergic activity may potentiate the anticholinergic effects of amantadine, and may increase the risk of antimuscarinic-related side effects. Additive drowsiness may also occur.
    Ambenonium Chloride: (Moderate) The therapeutic benefits of ambenonium may be diminished when coadministered with drugs known to exhibit anticholinergic properties including sedating H1-blockers. When concurrent use cannot be avoided, monitor the patient for reduced ambenonium efficacy.
    Amide local anesthetics: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Amikacin: (Minor) Chlorpheniramine may effectively mask vestibular symptoms (e.g. dizziness, tinnitus, or vertigo) that are associated with ototoxicity induced by aminoglycosides. Antiemetics block the histamine or acetylcholine response that causes nausea due to vestibular emetic stimuli such as motion.
    Amiloride: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when amiloride is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Amiloride; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone. (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when amiloride is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Aminoglycosides: (Minor) Chlorpheniramine may effectively mask vestibular symptoms (e.g. dizziness, tinnitus, or vertigo) that are associated with ototoxicity induced by aminoglycosides. Antiemetics block the histamine or acetylcholine response that causes nausea due to vestibular emetic stimuli such as motion.
    Amiodarone: (Moderate) Concomitant use of codeine with amiodarone may alter codeine plasma concentrations, resulting in an unpredictable effect such as reduced efficacy or symptoms of opioid withdrawal or prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage adjustment of codeine until stable drug effects are achieved. Discontinuation of amiodarone could alter codeine plasma concentrations, resulting in an unpredictable effect such as prolonged opioid adverse reactions or decreased opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If amiodarone is discontinued, monitor the patient carefully and consider adjusting the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amiodarone is a moderate inhibitor of CYP3A4 and CYP2D6. CYP3A4 inhibitors may increase codeine-related adverse effects while CYP2D6 inhibitors may reduce efficacy.
    Amitriptyline: (Major) Concomitant use of opioid agonists with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of opioid pain medications with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. Avoid prescribing opioid cough medication in patients taking tricyclic antidepressants.
    Amlodipine: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Atorvastatin: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Benazepril: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Celecoxib: (Moderate) A dosage adjustment may be warranted for chlorpheniramine if coadministered with celecoxib due to the potential for celecoxib to enhance the exposure and toxicity of chlorpheniramine. Celecoxib is a CYP2D6 inhibitor, and chlorpheniramine is a CYP2D6 substrate. (Moderate) Concomitant use of codeine with celecoxib may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of celecoxib could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If celecoxib is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Celecoxib is an inhibitor of CYP2D6. (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Olmesartan: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Valsartan: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations.
    Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for an increase in codeine-related adverse reactions including sedation and respiratory depression if coadministration with amlodipine is necessary; adjust the dose of codeine if necessary. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Amlodipine is a weak CYP3A4 inhibitor. Concomitant use may result in an increase in codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and increased morphine concentrations. (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Amobarbital: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Amoxapine: (Major) Concomitant use of opioid agonists with amoxapine may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking amoxapine. Limit the use of opioid pain medications with amoxapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. (Moderate) Additive anticholinergic effects may be seen when amoxapine is used concomitantly with drugs are known to possess relatively significant antimuscarinic properties, including sedating H1-blockers. Antimuscarinic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature Additive sedation may also occur.
    Amoxicillin; Clarithromycin; Omeprazole: (Moderate) Concomitant use of codeine with clarithromycin may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of clarithromycin could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If clarithromycin is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Clarithromycin is a strong inhibitor of CYP3A4.
    Amphetamine: (Moderate) Amphetamines may pharmacodynamically counteract the sedative properties of some antihistamines, such as the sedating H1-blockers (i.e., diphenhydramine). This effect may be clinically important if a patient is receiving an antihistamine agent for treatment of insomnia. Alternatively, if a patient is receiving an amphetamine for treatment of narcolepsy, the combination with a sedating antihistamine may reverse the action of the amphetamine. (Moderate) If concomitant use of codeine and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
    Amphetamine; Dextroamphetamine Salts: (Moderate) Amphetamines may pharmacodynamically counteract the sedative properties of some antihistamines, such as the sedating H1-blockers (i.e., diphenhydramine). This effect may be clinically important if a patient is receiving an antihistamine agent for treatment of insomnia. Alternatively, if a patient is receiving an amphetamine for treatment of narcolepsy, the combination with a sedating antihistamine may reverse the action of the amphetamine.
    Amphetamine; Dextroamphetamine: (Moderate) Amphetamines may pharmacodynamically counteract the sedative properties of some antihistamines, such as the sedating H1-blockers (i.e., diphenhydramine). This effect may be clinically important if a patient is receiving an antihistamine agent for treatment of insomnia. Alternatively, if a patient is receiving an amphetamine for treatment of narcolepsy, the combination with a sedating antihistamine may reverse the action of the amphetamine. (Moderate) If concomitant use of codeine and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
    Amphetamines: (Moderate) If concomitant use of codeine and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
    Anticholinergics: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Apalutamide: (Moderate) Concomitant use of codeine with apalutamide can decrease codeine levels, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor for reduced efficacy of codeine and signs of opioid withdrawal; consider increasing the dose of codeine as needed. If apalutamide is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Apalutamide is a strong CYP3A4 inducer.
    Apomorphine: (Major) Concomitant use of opioid agonists with apomorphine may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking apomorphine. Limit the use of opioid pain medications with apomorphine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Dopaminergic agents like apomorphine have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Prescribers should re-assess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment. (Moderate) Apomorphine causes significant somnolence. Concomitant administration of apomorphine and chlorpheniramine could result in additive depressant effects. Careful monitoring is recommended during combined use. A dose reduction of one or both drugs may be warranted.
    Apraclonidine: (Minor) Theoretically, apraclonidine might potentiate the effects of CNS depressant drugs such as opiate agonists. Although no specific drug interactions were identified with systemic agents and apraclonidine during clinical trials, apraclonidine can cause dizziness and somnolence.
    Aprepitant, Fosaprepitant: (Moderate) Concomitant use of codeine with oral, multi-day regimens of aprepitant, fosaprepitant may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of aprepitant, fosaprepitant could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If aprepitant, fosaprepitant is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Aprepitant, fosaprepitant, when administered as an oral, 3-day regimen, is a moderate inhibitor of CYP3A4.
    Aripiprazole: (Moderate) Concomitant use of opioid agonists with aripiprazole may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking aripiprazole. Limit the use of opioid pain medications with aripiprazole to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
    Artemether; Lumefantrine: (Moderate) Concomitant use of codeine with lumefantrine may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of lumefantrine could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If lumefantrine is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Lumefantrine is a moderate inhibitor of CYP2D6. (Moderate) Lumefantrine is an inhibitor and chlorpheniramine is a substrate/inhibitor of the CYP2D6 isoenzyme; therefore, coadministration may lead to increased chlorpheniramine concentrations. Concomitant use warrants caution due to the potential for increased side effects.
    Articaine; Epinephrine: (Moderate) Chlorpheniramine may potentiate the arrhythmogenic effects of epinephrine. (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Asciminib: (Moderate) Concomitant use of codeine with asciminib may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of asciminib could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If asciminib is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A to norcodeine; norcodeine does not have analgesic properties. Asciminib is a weak inhibitor of CYP3A.
    Asenapine: (Moderate) Concomitant use of opioid agonists with asenapine may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking asenapine. Limit the use of opioid pain medications with asenapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. (Moderate) Using drugs that can cause CNS depression, such as sedating H1-blockers, concomitantly with asenapine may increase both the frequency and the intensity of adverse effects such as drowsiness, sedation, and dizziness.
    Aspirin, ASA; Butalbital; Caffeine: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Aspirin, ASA; Butalbital; Caffeine; Codeine: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Aspirin, ASA; Caffeine; Dihydrocodeine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Aspirin, ASA; Caffeine; Orphenadrine: (Major) Concomitant use of opioid agonists with orphenadrine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with orphenadrine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking orphenadrine. (Moderate) Additive anticholinergic effects may be seen when drugs with anticholinergic properties, like sedating H1-blockers and orphenadrine, are used concomitantly. Adverse effects may be seen not only on GI smooth muscle, but also on bladder function, the CNS, the eye, and temperature regulation. Additive drowsiness may also occur.
    Aspirin, ASA; Carisoprodol: (Major) Concomitant use of opioid agonists with carisoprodol may cause excessive sedation and somnolence. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking carisoprodol. (Moderate) Carisoprodol is metabolized to meprobamate, a significant CNS depressant. Carisoprodol can cause additive CNS depression if used concomitantly with other CNS depressants. Additive effects of sedation and dizziness, which can impair the ability to undertake tasks requiring mental alertness, may occur if carisoprodol is taken with sedating H1-blockers. Utilize appropriate caution if carisoprodol is coadministered with another CNS depressant.
    Aspirin, ASA; Carisoprodol; Codeine: (Major) Concomitant use of opioid agonists with carisoprodol may cause excessive sedation and somnolence. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking carisoprodol. (Moderate) Carisoprodol is metabolized to meprobamate, a significant CNS depressant. Carisoprodol can cause additive CNS depression if used concomitantly with other CNS depressants. Additive effects of sedation and dizziness, which can impair the ability to undertake tasks requiring mental alertness, may occur if carisoprodol is taken with sedating H1-blockers. Utilize appropriate caution if carisoprodol is coadministered with another CNS depressant. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Aspirin, ASA; Oxycodone: (Major) Concomitant use of oxycodone with other opiate agonists may lead to additive respiratory and/or CNS depression. Hypotension, profound sedation, coma, respiratory depression, or death may occur. Prior to concurrent use of oxycodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. If a CNS depressant is used concurrently with oxycodone, a reduced dosage of oxycodone and/or the CNS depressant is recommended; use an initial dose of oxycodone at 1/3 to 1/2 the usual dosage. Monitor for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Atazanavir: (Moderate) Concomitant use of codeine with atazanavir may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of atazanavir could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If atazanavir is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Atazanavir is a strong inhibitor of CYP3A4.
    Atazanavir; Cobicistat: (Moderate) Caution is warranted when cobicistat is administered with chlorpheniramine as there is a potential for elevated chlorpheniramine and cobicistat concentrations. Chlorpheniramine is a CYP2D6 substrate/inhibitor. Cobicistat is a substrate/inhibitor of CYP2D6. (Moderate) Concomitant use of codeine with atazanavir may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of atazanavir could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If atazanavir is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Atazanavir is a strong inhibitor of CYP3A4. (Moderate) Concomitant use of codeine with cobicistat may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of cobicistat could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If cobicistat is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Cobicistat is a strong inhibitor of CYP3A4.
    Atenolol; Chlorthalidone: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Atropine; Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Contraindicated) Codeine use in patients taking methylene blue or within 14 days of stopping such treatment is contraindicated due to the risk of serotonin syndrome or opioid toxicity. If urgent use of an opioid is necessary, use test doses and frequent titration of small doses of another opioid to treat pain while closely monitoring blood pressure and signs and symptoms of CNS and respiratory depression.
    Atropine; Difenoxin: (Moderate) An enhanced CNS depressant effect may occur when diphenoxylate/difenoxin is combined with other CNS depressants. Diphenoxylate/difenoxin decreases GI motility. Other drugs that also decrease GI motility, such as sedating H1 blockers, may produce additive effects with diphenoxylate/difenoxin if used concomitantly. (Moderate) Concurrent administration of diphenoxylate/difenoxin with other opiate agonists can potentiate the CNS-depressant effects of diphenoxylate/difenoxin. Use caution during coadministration. In addition, diphenoxylate/difenoxin use may cause constipation; cases of severe GI reactions including toxic megacolon and adynamic ileus have been reported. Reduced GI motility when combined with opiate agonists may increase the risk of serious GI related adverse events.
    Avacopan: (Moderate) Concomitant use of codeine with avacopan may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of avacopan could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If avacopan is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A to norcodeine; norcodeine does not have analgesic properties. Avacopan is a weak inhibitor of CYP3A.
    Azelastine: (Major) An enhanced CNS depressant effect may occur when azelastine is combined with other CNS depressants including sedating H1-blockers; avoid concurrent use. (Major) Concomitant use of opioid agonists with azelastine may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking azelastine. Limit the use of opioid pain medications with azelastine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
    Azelastine; Fluticasone: (Major) An enhanced CNS depressant effect may occur when azelastine is combined with other CNS depressants including sedating H1-blockers; avoid concurrent use. (Major) Concomitant use of opioid agonists with azelastine may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking azelastine. Limit the use of opioid pain medications with azelastine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
    Azilsartan; Chlorthalidone: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Baclofen: (Major) Concomitant use of opioid agonists with baclofen may cause excessive sedation and somnolence. Limit the use of opioid pain medications with baclofen to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking baclofen. (Moderate) An enhanced CNS depressant effect may occur when sedating H1-blockers are combined with other CNS depressants including skeletal muscle relaxants, such as baclofen.
    Barbiturates: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Belladonna; Opium: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Belumosudil: (Moderate) Concomitant use of codeine with belumosudil may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of belumosudil could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If belumosudil is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A to norcodeine; norcodeine does not have analgesic properties. Belumosudil is a weak inhibitor of CYP3A.
    Belzutifan: (Moderate) Monitor for reduced efficacy of codeine and signs of opioid withdrawal in patients who have developed physical dependence if coadministration with belzutifan is necessary; consider increasing the dose of codeine as needed. It is recommended to avoid this combination when codeine is being used for cough. If belzutifan is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A to norcodeine; norcodeine does not have analgesic properties. Belzutifan is a weak CYP3A inducer. Concomitant use with belzutifan can increase norcodeine levels via increased CYP3A metabolism, resulting in decreased metabolism via CYP2D6 resulting in lower morphine levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
    Benazepril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Bendroflumethiazide; Nadolol: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Benzhydrocodone; Acetaminophen: (Major) Concomitant use of opioid agonists with benzhydrocodone may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of benzhydrocodone with opioid agonists to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If benzhydrocodone is initiated in a patient taking codeine, reduce initial dosage and titrate to clinical response. If codeine is prescribed in a patient taking benzhydrocodone, use a lower initial dose of codeine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Avoid prescribing opioid cough medications in patients taking other opioid agonists. Careful monitoring, particularly during treatment initiation and dose adjustment, is recommended during coadministration of benzhydrocodone and codeine because of the potential risk of serotonin syndrome. Discontinue benzhydrocodone if serotonin syndrome is suspected. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Benzodiazepines: (Moderate) Coadministration can potentiate the CNS effects (e.g., increased sedation or respiratory depression) of either agent. Use caution with this combination.
    Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Contraindicated) Codeine use in patients taking methylene blue or within 14 days of stopping such treatment is contraindicated due to the risk of serotonin syndrome or opioid toxicity. If urgent use of an opioid is necessary, use test doses and frequent titration of small doses of another opioid to treat pain while closely monitoring blood pressure and signs and symptoms of CNS and respiratory depression.
    Benzonatate: (Moderate) The vagal effects and respiratory depression induced by opiate agonists may be increased by the use of benzonatate.
    Benzphetamine: (Moderate) Amphetamines may pharmacodynamically counteract the sedative properties of some antihistamines, such as the sedating H1-blockers. This effect may be clinically important if a patient is receiving an antihistamine agent for treatment of insomnia. Alternatively, if a patient is receiving an amphetamine for treatment of narcolepsy, the combination with a sedating antihistamine may reverse the action of the amphetamine. (Moderate) If concomitant use of codeine and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
    Berotralstat: (Moderate) Concomitant use of codeine with berotralstat may alter codeine plasma concentrations, resulting in an unpredictable effect such as reduced efficacy or symptoms of opioid withdrawal or prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage adjustment of codeine until stable drug effects are achieved. Discontinuation of berotralstat could alter codeine plasma concentrations, resulting in an unpredictable effect such as prolonged opioid adverse reactions or decreased opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If berotralstat is discontinued, monitor the patient carefully and consider adjusting the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Berotralstat is a moderate inhibitor of CYP3A4 and CYP2D6. CYP3A4 inhibitors may increase codeine-related adverse effects while CYP2D6 inhibitors may reduce efficacy.
    Bethanechol: (Moderate) Bethanechol facilitates intestinal and bladder function via parasympathomimetic actions. Opiate agonists impair the peristaltic activity of the intestine. Thus, these drugs can antagonize the beneficial actions of bethanechol on GI motility.
    Bexarotene: (Moderate) Concomitant use of codeine with bexarotene can decrease codeine levels, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor for reduced efficacy of codeine and signs of opioid withdrawal; consider increasing the dose of codeine as needed. If bexarotene is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Bexarotene is a moderate CYP3A4 inducer.
    Bismuth Subcitrate Potassium; Metronidazole; Tetracycline: (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Bismuth Subsalicylate: (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Bismuth Subsalicylate; Metronidazole; Tetracycline: (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Bisoprolol; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Bosentan: (Moderate) Concomitant use of codeine with bosentan can decrease codeine levels, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor for reduced efficacy of codeine and signs of opioid withdrawal; consider increasing the dose of codeine as needed. If bosentan is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Bosentan is a moderate CYP3A4 inducer.
    Brexpiprazole: (Major) Concomitant use of opioid agonists with brexpiprazole may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking brexpiprazole. Limit the use of opioid pain medications with brexpiprazole to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
    Brigatinib: (Moderate) Monitor for reduced efficacy of codeine and signs of opioid withdrawal in patients who have developed physical dependence if coadministration with brigatinib is necessary; consider increasing the dose of codeine as needed. It is recommended to avoid this combination when codeine is being used for cough. If brigatinib is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. brigatinib is a weak CYP3A4 inducer. Concomitant use with brigatinib can increase norcodeine levels via increased CYP3A4 metabolism, resulting in decreased metabolism via CYP2D6 resulting in lower morphine levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
    Brimonidine: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
    Brimonidine; Brinzolamide: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
    Brimonidine; Timolol: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
    Brompheniramine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Carbetapentane; Phenylephrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Brompheniramine; Dextromethorphan; Guaifenesin: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Dextromethorphan; Phenylephrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Guaifenesin; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Brompheniramine; Pseudoephedrine; Dextromethorphan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Bumetanide: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a loop diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Bupivacaine Liposomal: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Bupivacaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Bupivacaine; Lidocaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Bupivacaine; Meloxicam: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic may allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Buprenorphine: (Major) Buprenorphine is a mixed opiate agonist/antagonist with strong affinity for the mu-receptor that may partially block the effects of full mu-receptor opiate agonists and reduce analgesic effects. In some cases of acute pain, trauma, or during surgical management, opiate-dependent patients receiving buprenorphine maintenance therapy may require concurrent treatment with opiate agonists, such as codeine. In these cases, health care professionals must exercise caution in opiate agonist dose selection, as higher doses of an opiate agonist may be required to compete with buprenorphine at the mu-receptor. Management strategies may include adding a short-acting opiate agonist to achieve analgesia in the presence of buprenorphine, discontinuation of buprenorphine and use of an opiate agonist to avoid withdrawal and achieve analgesia, or conversion of buprenorphine to methadone while using additional opiate agonists if needed. Closely monitor patients for CNS or respiratory depression. When buprenorphine is used for analgesia, avoid co-use with opiate agonists. Buprenorphine may cause withdrawal symptoms in patients receiving chronic opiate agonists as well as possibly potentiate CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) If concurrent use of sedating H1-blockers and buprenorphine is necessary, consider a dose reduction of one or both drugs because of the potential for additive pharmacological effects. Hypotension, profound sedation, coma, respiratory depression, or death may occur during co-administration of buprenorphine and other CNS depressants. Prior to concurrent use of buprenorphine in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Evaluate the patient's use of alcohol or illicit drugs. It is recommended that the injectable buprenorphine dose be halved for patients who receive other drugs with CNS depressant effects; for the buprenorphine transdermal patch, start with the 5 mcg/hour patch. Monitor patients for sedation or respiratory depression.
    Buprenorphine; Naloxone: (Major) Buprenorphine is a mixed opiate agonist/antagonist with strong affinity for the mu-receptor that may partially block the effects of full mu-receptor opiate agonists and reduce analgesic effects. In some cases of acute pain, trauma, or during surgical management, opiate-dependent patients receiving buprenorphine maintenance therapy may require concurrent treatment with opiate agonists, such as codeine. In these cases, health care professionals must exercise caution in opiate agonist dose selection, as higher doses of an opiate agonist may be required to compete with buprenorphine at the mu-receptor. Management strategies may include adding a short-acting opiate agonist to achieve analgesia in the presence of buprenorphine, discontinuation of buprenorphine and use of an opiate agonist to avoid withdrawal and achieve analgesia, or conversion of buprenorphine to methadone while using additional opiate agonists if needed. Closely monitor patients for CNS or respiratory depression. When buprenorphine is used for analgesia, avoid co-use with opiate agonists. Buprenorphine may cause withdrawal symptoms in patients receiving chronic opiate agonists as well as possibly potentiate CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) If concurrent use of sedating H1-blockers and buprenorphine is necessary, consider a dose reduction of one or both drugs because of the potential for additive pharmacological effects. Hypotension, profound sedation, coma, respiratory depression, or death may occur during co-administration of buprenorphine and other CNS depressants. Prior to concurrent use of buprenorphine in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Evaluate the patient's use of alcohol or illicit drugs. It is recommended that the injectable buprenorphine dose be halved for patients who receive other drugs with CNS depressant effects; for the buprenorphine transdermal patch, start with the 5 mcg/hour patch. Monitor patients for sedation or respiratory depression.
    Bupropion: (Moderate) Concomitant use of codeine with bupropion may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of bupropion could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If bupropion is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Bupropion is a strong inhibitor of CYP2D6.
    Bupropion; Naltrexone: (Major) When naltrexone is used as adjuvant treatment of opiate or alcohol dependence, use is contraindicated in patients currently receiving opiate agonists. Naltrexone will antagonize the therapeutic benefits of opiate agonists and will induce a withdrawal reaction in patients with physical dependence to opioids. An opiate antagonist should only be administered to a patient taking codeine with clinically significant respiratory or cardiovascular depression. Also, patients should be opiate-free for at least 7-10 days prior to initiating naltrexone therapy. If there is any question of opioid use in the past 7-10 days and the patient is not experiencing opioid withdrawal symptoms and/or the urine is negative for opioids, a naloxone challenge test needs to be performed. If a patient receives naltrexone, and an opiate agonist is needed for an emergency situation, large doses of opiate agonists may ultimately overwhelm naltrexone antagonism of opiate receptors. Immediately following administration of exogenous opiate agonists, the opiate plasma concentration may be sufficient to overcome naltrexone competitive blockade, but the patient may experience deeper and more prolonged respiratory depression and thus, may be in danger of respiratory arrest and circulatory collapse. Non-receptor mediated actions like facial swelling, itching, generalized erythema, or bronchoconstriction may occur presumably due to histamine release. A rapidly acting opiate agonist is preferred as the duration of respiratory depression will be shorter. Patients receiving naltrexone may also experience opiate side effects with low doses of opiate agonists. If the opiate agonist is taken in such a way that high concentrations remain in the body beyond the time naltrexone exerts its therapeutic effects, serious side effects may occur. (Moderate) Concomitant use of codeine with bupropion may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of bupropion could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If bupropion is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Bupropion is a strong inhibitor of CYP2D6.
    Buspirone: (Moderate) Concomitant use of CNS depressants, such as buspirone, can potentiate the effects of codeine, which may potentially lead to respiratory depression, CNS depression, sedation, or hypotensive responses. If concurrent use of codeine and buspirone is imperative, reduce the dose of one or both drugs. (Moderate) The combination of buspirone and other CNS depressants, such as the sedating H1-blockers (sedating antihistamines), may increase the risk for sedation.
    Butabarbital: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Butalbital; Acetaminophen: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Butalbital; Acetaminophen; Caffeine: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities.
    Butalbital; Acetaminophen; Caffeine; Codeine: (Major) Concomitant use of codeine with barbiturates may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with barbiturates to only patients for whom alternative treatment options are inadequate. It is recommended to avoid this combination when codeine is being used for cough. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concomitant use of codeine with a barbiturate can decrease codeine concentrations, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Monitor for reduced efficacy of codeine and signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates induce CYP3A4. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. (Moderate) Additive CNS depression may occur if barbiturates are co-used with sedating antihistamines, such as chlorpheniramine. Monitor for additive CNS and respiratory effects, and warn about the potential effects to driving and other activities. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Butorphanol: (Major) Avoid the concomitant use of butorphanol and opiate agonists, such as codeine. Butorphanol is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of codeine. Butorphanol may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of butorphanol with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Concomitant use of butorphanol with sedating H1-blockers can potentiate the effects of butorphanol on CNS and/or respiratory depression. Use together with caution. If a CNS depressant needs to be used with butorphanol, use the smallest effective dose and the longest dosing frequency of butorphanol.
    Calcium, Magnesium, Potassium, Sodium Oxybates: (Major) Concomitant use of opioid agonists with sodium oxybate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medication with sodium oxybate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
    Candesartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Cannabidiol: (Moderate) Concomitant use of opioid agonists with cannabidiol may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking cannabidiol. Limit the use of opioid pain medications with cannabidiol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. (Moderate) Monitor for excessive sedation and somnolence during coadministration of cannabidiol and sedating H1-blockers. CNS depressants can potentiate the effects of cannabidiol.
    Capsaicin; Metaxalone: (Major) Concomitant use of opioid agonists with metaxalone may cause excessive sedation and somnolence. Limit the use of opioid pain medications with metaxalone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking metaxalone. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. (Moderate) Concomitant administration of metaxalone with other CNS depressants can potentiate the sedative effects of either agent.
    Captopril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Carbamazepine: (Moderate) Concomitant use of codeine with carbamazepine can decrease codeine levels, resulting in less metabolism by CYP2D6 and decreased morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor for reduced efficacy of codeine and signs of opioid withdrawal; consider increasing the dose of codeine as needed. If carbamazepine is discontinued, consider a dose reduction of codeine and frequently monitor for signs or respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Carbamazepine is a strong CYP3A4 inducer.
    Carbetapentane; Chlorpheniramine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Chlorpheniramine; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with diphenhydramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with diphenhydramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Guaifenesin: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Guaifenesin; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Phenylephrine; Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Pseudoephedrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbetapentane; Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including sedating h1-blockers. (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including morphine.
    Carbidopa; Levodopa; Entacapone: (Moderate) COMT inhibitors should be given cautiously with other agents that cause CNS depression, including sedating H1-blockers, due to the possibility of additive sedation. COMT inhibitors have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Prescribers should re-assess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment. Patients should be advised to avoid driving or other tasks requiring mental alertness until they know how the combination affects them.
    Carbinoxamine: (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Carbinoxamine; Dextromethorphan; Pseudoephedrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Carbinoxamine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Carbinoxamine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Cariprazine: (Moderate) Concomitant use of opioid agonists lik codeine with cariprazine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with cariprazine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Avoid prescribing opioid cough medication in patients taking cariprazine.
    Carisoprodol: (Major) Concomitant use of opioid agonists with carisoprodol may cause excessive sedation and somnolence. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Avoid prescribing opioid cough medication in patients taking carisoprodol. (Moderate) Carisoprodol is metabolized to meprobamate, a significant CNS depressant. Carisoprodol can cause additive CNS depression if used concomitantly with other CNS depressants. Additive effects of sedation and dizziness, which can impair the ability to undertake tasks requiring mental alertness, may occur if carisoprodol is taken with sedating H1-blockers. Utilize appropriate caution if carisoprodol is coadministered with another CNS depressant.
    Celecoxib: (Moderate) A dosage adjustment may be warranted for chlorpheniramine if coadministered with celecoxib due to the potential for celecoxib to enhance the exposure and toxicity of chlorpheniramine. Celecoxib is a CYP2D6 inhibitor, and chlorpheniramine is a CYP2D6 substrate. (Moderate) Concomitant use of codeine with celecoxib may increase codeine plasma concentrations, but decrease the plasma concentration of the active metabolite, morphine, resulting in reduced efficacy or symptoms of opioid withdrawal. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage increase of codeine until stable drug effects are achieved. Discontinuation of celecoxib could decrease codeine plasma concentrations and increase morphine plasma concentrations resulting in prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If celecoxib is discontinued, monitor the patient carefully and consider reducing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Celecoxib is an inhibitor of CYP2D6.
    Cenobamate: (Moderate) Concomitant use of codeine with cenobamate may cause excessive sedation and somnolence. Limit the use of codeine with cenobamate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Avoid prescribing codeine cough medication in patients taking cenobamate. Additionally, monitor for reduced efficacy of codeine and signs of opioid withdrawal in patients who have developed physical dependence if coadministration with cenobamate is necessary; consider increasing the dose of codeine as needed. If cenobamate is discontinued, consider a dose reduction of codeine and frequently monitor for signs of respiratory depression and sedation. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Cenobamate is a moderate CYP3A4 inducer. Concomitant use with cenobamate can increase norcodeine concentrations via increased CYP3A4 metabolism, resulting in decreased metabolism via CYP2D6 resulting in lower morphine concentrations; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. (Moderate) Monitor for excessive sedation and somnolence during coadministration of cenobamate and sedating H1-blockers. Concurrent use may result in additive CNS depression.
    Ceritinib: (Moderate) Concomitant use of codeine with ceritinib may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6 and, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of ceritinib could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If ceritinib is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Ceritinib is a strong inhibitor of CYP3A4.
    Cetirizine: (Moderate) Concomitant use of opioid agonists with cetirizine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with cetirizine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Due to the duplicative and additive pharmacology, concurrent use of cetirizine/levocetirizine with sedating H1-blockers should generally be avoided. Coadministration may increase the risk of anticholinergic and CNS depressant-related side effects. If concurrent use is necessary, monitor for excessive anticholinergic effects, sedation, and somnolence.
    Cetirizine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with cetirizine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with cetirizine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. (Moderate) Due to the duplicative and additive pharmacology, concurrent use of cetirizine/levocetirizine with sedating H1-blockers should generally be avoided. Coadministration may increase the risk of anticholinergic and CNS depressant-related side effects. If concurrent use is necessary, monitor for excessive anticholinergic effects, sedation, and somnolence.
    Chlophedianol; Dexbrompheniramine: (Moderate) Concomitant use of opioid agonists with dexbrompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexbrompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with dexchlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexchlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Chloral Hydrate: (Major) Concomitant use of opioid agonists with chloral hydrate may cause excessive sedation and somnolence. Avoid prescribing opioid cough medications in patients taking chloral hydrate. Limit the use of opioid pain medications with chloral hydrate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
    Chloramphenicol: (Moderate) Concomitant use of codeine with chloramphenicol may increase codeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased morphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. It is recommended to avoid this combination when codeine is being used for cough. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of codeine until stable drug effects are achieved. Discontinuation of chloramphenicol could decrease codeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to codeine. If chloramphenicol is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Codeine is primarily metabolized by CYP2D6 to morphine, and by CYP3A4 to norcodeine; norcodeine does not have analgesic properties. Chloramphenicol is a strong inhibitor of CYP3A4.
    Chlorcyclizine: (Moderate) Concomitant use of opioid agonists with chlorcyclizine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorcyclizine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Chlordiazepoxide: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If an opiate agonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the opiate and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Avoid prescribing opiate cough medications in patients taking benzodiazepines.
    Chlordiazepoxide; Amitriptyline: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If an opiate agonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the opiate and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Avoid prescribing opiate cough medications in patients taking benzodiazepines. (Major) Concomitant use of opioid agonists with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of opioid pain medications with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. Avoid prescribing opioid cough medication in patients taking tricyclic antidepressants.
    Chlordiazepoxide; Clidinium: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If an opiate agonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the opiate and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Avoid prescribing opiate cough medications in patients taking benzodiazepines.
    Chloroprocaine: (Minor) Due to the CNS depression potential of all local anesthetics, they should be used with caution with other agents that can cause respiratory depression, such as opiate agonists.
    Chlorothiazide: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when a thiazide diuretic is administered with codeine. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
    Chlorpheniramine; Dextromethorphan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering codeine with dextromethorphan. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently r