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    Nucleoside and Nucleotide Analog Antivirals for Hepatitis B

    BOXED WARNING

    Hepatitis B exacerbation

    Severe acute hepatitis B exacerbation (with ALT elevations 10 times the upper limit of normal or greater) has been reported in up to 25% of patients who have discontinued anti-hepatitis B therapy with adefovir; most events occurred within 12 weeks of drug discontinuation. Such exacerbations were generally found to occur in the absence of HBeAg seroconversion, and presented as serum ALT elevations in addition to reemergence of viral replication. Patients with advanced liver disease or cirrhosis may be at higher risk for hepatic decompensation, although, in the HBeAg-positive and HBeAg-negative studies in patients with compensated liver function, the exacerbations were not generally accompanied by hepatic decompensation. While most events appear to have been self-limited or resolved with reinitiation of treatment, severe hepatitis exacerbations, including fatalities, have been reported. Patients who discontinue adefovir should have their hepatic function regularly monitored for at least several months; if appropriate, resumption of anti-hepatitis B therapy may be warranted.

    Dialysis, nephrotoxicity, renal disease, renal failure, renal impairment

    Adefovir may cause nephrotoxicity, particularly in patients with pre-existing renal disease, renal impairment, or renal failure. Creatinine clearance should be calculated in all patients prior to initiating therapy. Nephrotoxicity is the treatment-limiting toxicity of adefovir dipivoxil and is characterized by a delayed onset of gradual increases in serum creatinine and decreases in serum phosphorus. Historically, nephrotoxicity is dose-related and occurs at substantially higher doses (i.e., 60—500 mg/day for HIV or 30 mg/day for chronic hepatitis B) than those currently recommended (i.e., 10 mg/day PO). However, chronic administration of adefovir (10 mg once daily) may result in nephrotoxicity. The overall risk of nephrotoxicity in patients with adequate renal function is low. However, this is of special importance in patients at risk of or having underlying renal dysfunction and patients taking concomitant nephrotoxic agents. It is important to monitor renal function (e.g., serum creatinine, etc.) for all patients during treatment, particularly for those with risk factors for renal impairment. Patients with renal insufficiency or on dialysis at baseline or during treatment may require dosage adjustment (see Dosage). The risks and benefits of adefovir dipivoxil should be carefully evaluated prior to discontinuing treatment in a patient with treatment-emergent nephrotoxicity.

    Hepatitis B and HIV coinfection, human immunodeficiency virus (HIV) infection, human immunodeficiency virus (HIV) infection resistance

    Adefovir has some activity against the human immunodeficiency virus; patients being treated with adefovir who have unrecognized or untreated human immunodeficiency virus (HIV) infection are at risk of developing human immunodeficiency virus (HIV) infection resistance. Prior to initiating therapy, HIV antibody testing should be offered to all patients. Adefovir has not been shown to suppress HIV RNA in patients; however, there are limited data on its use to treat patients with chronic hepatitis B and HIV coinfection. HIV treatment guidelines recommend against use of adefovir (alone or in combination with lamivudine or emtricitabine) in patients with hepatitis B and HIV coinfection. Data regarding use of adefovir in these patients are limited; and compared with other treatment regimens, adefovir is associated with higher incidence of toxicities and increased rates of HBV treatment failure. Instead, guidelines recommend these patients receive a fully suppressive antiretroviral (ARV) regimen that contains a dual NRTI backbone of emtricitabine; tenofovir alafenamide or tenofovir disoproxil fumarate with either emtricitabine or lamivudine. If tenofovir cannot be used, entecavir should be given in combination with a fully suppressive ARV regimen (note: entecavir should not be considered part of the ARV regimen). Most coinfected patients should continue treatment indefinitely with the goal of maximal HIV suppression and prevention of HBV relapse. If treatment must be discontinued, monitor transaminase concentrations every 6 weeks for the first 3 months, and every 3 to 6 months thereafter. For patients who refuse a fully suppressive ARV regimen, but still requires treatment for HBV, consider 48 weeks of peginterferon alfa; do not administer HIV-active medications in the absence of a fully suppressive ARV regimen. Instruct patients to avoid consuming alcohol, and offer vaccinations against hepatitis A and hepatitis B as appropriate.

    Females, hepatic disease, Hepatotoxicity or Lactic Acidosis, obesity

    Hepatotoxicity or lactic acidosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals; patients who are concurrently taking adefovir with antiretrovirals are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. A majority of these cases have been in females; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Treatment with adefovir dipivoxil should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

    DEA CLASS

    Rx

    DESCRIPTION

    Acyclic nucleotide analog
    For the treatment of chronic hepatitis B virus (HBV) infections in patients 12 years and older
    Black Box Warnings for: nephrotoxicity; severe acute exacerbations of hepatitis; HIV resistance; lactic acidosis and severe hepatomegaly with steatosis

    COMMON BRAND NAMES

    Hepsera

    HOW SUPPLIED

    Adeforvir/Adefovir Dipivoxil/Hepsera Oral Tab: 10mg

    DOSAGE & INDICATIONS

    For the treatment of chronic hepatitis B infection.
    NOTE: In order to reduce the risk of resistance in patients with lamivudine-resistant hepatitis B virus, the manufacturer recommends using adefovir plus lamivudine.
    NOTE: In order to reduce the risk of resistance in all patients receiving adefovir monotherapy, the manufacturer recommends that hepatitis B treatment therapy with adefovir be potentially modified if serum hepatitis B virus DNA remains above 1000 copies/mL with continued treatment.
    Oral dosage
    Adults

    10 mg PO once daily. The optimal duration of treatment is not known.[28784] Due to higher incidence of toxicity and HBV treatment failure, guidelines recommend against the use of adefovir for the treatment of patients with HBV and HIV coinfection.[34362] [46638]

    Children and Adolescents 12 years and older

    10 mg PO once daily. The optimal duration of treatment is not known.[28784] In HBV and HIV coinfected patients, guidelines suggest treatment with adefovir for at least 12 months. Indications for treatment include a detectable serum HBV DNA with or without a positive HBeAg for more than 6 months; and persistent (more than 6 months) elevation of serum transaminases (2-times the upper limit of normal or higher) or evidence of chronic hepatitis on liver biopsy.[34361]

    MAXIMUM DOSAGE

    Adults

    10 mg/day PO.

    Geriatric

    10 mg/day PO.

    Adolescents

    10 mg/day PO.

    Children

    12 years: 10 mg/day PO.
    7 to 11 years: Safety and efficacy have not been established; doses up to 0.25 mg/kg/day (maximum 10 mg/day) PO have been used off-label for the treatment of chronic hepatitis B infection.
    2 to 6 years: Safety and efficacy have not been established; doses up to 0.3 mg/kg/day PO have been used off-label for the treatment of chronic hepatitis B infection.
    Younger than 2 years: Safety and efficacy have not been established.

    Infants

    Safety and efficacy have not been established.

    Neonates

    Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    No dosage adjustment needed.

    Renal Impairment

    NOTE: Dosing adjustments are for adult patients only. No clinical data are available to make dosing adjustment recommendations for pediatric patients with renal insufficiency.
    CrCl 50 mL/min or greater: No dosage adjustment needed.
    CrCl 30 to 49 mL/min: 10 mg PO every 48 hours.
    CrCl 10 to 29 mL/min: 10 mg PO every 72 hours.
    CrCl less than 10 mL/min: Adefovir has not been evaluated in non-hemodialysis patients with CrCl below 10 mL/min; no dosing recommendation is available.
     
    Intermittent hemodialysis
    Patients should receive 10 mg PO every 7 days, administered after hemodialysis.
     
    Peritoneal dialysis
    Insufficient data are available to recommend a dosage of adefovir in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

    ADMINISTRATION

    For storage information, see the specific information within the How Supplied section.

    Oral Administration

    Administer without regard to food.

    STORAGE

    Hepsera:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    - Store in original container

    CONTRAINDICATIONS / PRECAUTIONS

    Hepatitis B exacerbation

    Severe acute hepatitis B exacerbation (with ALT elevations 10 times the upper limit of normal or greater) has been reported in up to 25% of patients who have discontinued anti-hepatitis B therapy with adefovir; most events occurred within 12 weeks of drug discontinuation. Such exacerbations were generally found to occur in the absence of HBeAg seroconversion, and presented as serum ALT elevations in addition to reemergence of viral replication. Patients with advanced liver disease or cirrhosis may be at higher risk for hepatic decompensation, although, in the HBeAg-positive and HBeAg-negative studies in patients with compensated liver function, the exacerbations were not generally accompanied by hepatic decompensation. While most events appear to have been self-limited or resolved with reinitiation of treatment, severe hepatitis exacerbations, including fatalities, have been reported. Patients who discontinue adefovir should have their hepatic function regularly monitored for at least several months; if appropriate, resumption of anti-hepatitis B therapy may be warranted.

    Dialysis, nephrotoxicity, renal disease, renal failure, renal impairment

    Adefovir may cause nephrotoxicity, particularly in patients with pre-existing renal disease, renal impairment, or renal failure. Creatinine clearance should be calculated in all patients prior to initiating therapy. Nephrotoxicity is the treatment-limiting toxicity of adefovir dipivoxil and is characterized by a delayed onset of gradual increases in serum creatinine and decreases in serum phosphorus. Historically, nephrotoxicity is dose-related and occurs at substantially higher doses (i.e., 60—500 mg/day for HIV or 30 mg/day for chronic hepatitis B) than those currently recommended (i.e., 10 mg/day PO). However, chronic administration of adefovir (10 mg once daily) may result in nephrotoxicity. The overall risk of nephrotoxicity in patients with adequate renal function is low. However, this is of special importance in patients at risk of or having underlying renal dysfunction and patients taking concomitant nephrotoxic agents. It is important to monitor renal function (e.g., serum creatinine, etc.) for all patients during treatment, particularly for those with risk factors for renal impairment. Patients with renal insufficiency or on dialysis at baseline or during treatment may require dosage adjustment (see Dosage). The risks and benefits of adefovir dipivoxil should be carefully evaluated prior to discontinuing treatment in a patient with treatment-emergent nephrotoxicity.

    Hepatitis B and HIV coinfection, human immunodeficiency virus (HIV) infection, human immunodeficiency virus (HIV) infection resistance

    Adefovir has some activity against the human immunodeficiency virus; patients being treated with adefovir who have unrecognized or untreated human immunodeficiency virus (HIV) infection are at risk of developing human immunodeficiency virus (HIV) infection resistance. Prior to initiating therapy, HIV antibody testing should be offered to all patients. Adefovir has not been shown to suppress HIV RNA in patients; however, there are limited data on its use to treat patients with chronic hepatitis B and HIV coinfection. HIV treatment guidelines recommend against use of adefovir (alone or in combination with lamivudine or emtricitabine) in patients with hepatitis B and HIV coinfection. Data regarding use of adefovir in these patients are limited; and compared with other treatment regimens, adefovir is associated with higher incidence of toxicities and increased rates of HBV treatment failure. Instead, guidelines recommend these patients receive a fully suppressive antiretroviral (ARV) regimen that contains a dual NRTI backbone of emtricitabine; tenofovir alafenamide or tenofovir disoproxil fumarate with either emtricitabine or lamivudine. If tenofovir cannot be used, entecavir should be given in combination with a fully suppressive ARV regimen (note: entecavir should not be considered part of the ARV regimen). Most coinfected patients should continue treatment indefinitely with the goal of maximal HIV suppression and prevention of HBV relapse. If treatment must be discontinued, monitor transaminase concentrations every 6 weeks for the first 3 months, and every 3 to 6 months thereafter. For patients who refuse a fully suppressive ARV regimen, but still requires treatment for HBV, consider 48 weeks of peginterferon alfa; do not administer HIV-active medications in the absence of a fully suppressive ARV regimen. Instruct patients to avoid consuming alcohol, and offer vaccinations against hepatitis A and hepatitis B as appropriate.

    Females, hepatic disease, Hepatotoxicity or Lactic Acidosis, obesity

    Hepatotoxicity or lactic acidosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals; patients who are concurrently taking adefovir with antiretrovirals are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. A majority of these cases have been in females; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Treatment with adefovir dipivoxil should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

    Pregnancy

    Adequate and well-controlled studies have not been conducted regarding the use of adefovir during human pregnancy; and prospective data from the Antiretroviral Pregnancy Registry (APR) are insufficient to adequately assess the risk of birth defects, miscarriages, or adverse maternal or fetal outcomes. Reproductive studies in rats and rabbits have shown no embryotoxicity or teratogenicity when given orally at systemic doses greater than 20-times the normal human dose. However, embryotoxicity and fetal malformations were observed in the offspring of rats who were administered intravenous doses greater that 35-times the normal human dose. Because animal reproduction studies are not always predictive of human response, adefovir should be used during pregnancy only if clearly needed and after careful consideration of the risks and benefits. To monitor fetal outcomes of pregnant women exposed to adefovir, a pregnancy registry has been established. It is strongly recommended that health care providers who are treating pregnant women and their newborns report cases of prenatal exposure to adefovir to the Antiretroviral Pregnancy Registry by calling 1-800-258-4263.[27468] There are no data on the effect of adefovir on the transmission of HBV from mother to infant during labor and obstetric delivery; therefore, appropriate immunizations against HBV should be used to prevent neonatal acquisition of hepatitis B virus after birth, in accordance with current guidelines.[28784]

    Breast-feeding

    It is not known whether adefovir is excreted in human breast milk, affects milk production, or has an adverse effect on breast-fed infants. Antiviral medications whose passage into human breast milk have been evaluated include tenofovir and lamivudine. Healthcare providers have not reached a consensus regarding breast-feeding and treatment of HBV infections. In a survey of 226 physicians, 30.5% would recommend breast-feeding for HBV-infected mothers on antiviral therapy, 44% would not recommend breast-feeding during antiviral therapy, and 25.2% stated they were unsure. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.[28784] [46710] [46680] [46688]

    Children, infants, neonates

    Safety and efficacy of adefovir dipivoxil in neonates, infants, and children < 12 years has not been established.

    Geriatric

    Caution should be exercised when prescribing adefovir dipivoxil to geriatric patients since they have greater frequency of decreased renal or cardiac function due to concomitant disease or other drug therapy.

    Liver transplant

    Adverse reactions such as abnormal renal function, renal failure, vomiting, rash, and pruritus were observed among pre- (n = 226) and post- (n = 241) liver transplant patients with chronic hepatitis B and clinical evidence of lamivudine-resistant hepatitis B virus who received open-label adefovir for up to 203 weeks (median time on treatment of 51 and 99 weeks, respectively). Changes in renal function occurred in pre- and post-liver transplant patients who had risk factors for renal dysfunction including concomitant use of cyclosporine and tacrolimus, renal insufficiency at baseline, hypertension, diabetes, and on-study organ transplantation. Therefore, the contribution of adefovir treatment to the changes in renal function is difficult to assess.

    ADVERSE REACTIONS

    Severe

    hepatitis B exacerbation / Delayed / 25.0-25.0
    Fanconi syndrome / Delayed / Incidence not known
    nephrotoxicity / Delayed / Incidence not known
    azotemia / Delayed / Incidence not known
    renal failure (unspecified) / Delayed / Incidence not known
    bone fractures / Delayed / Incidence not known
    lactic acidosis / Delayed / Incidence not known
    hepatotoxicity / Delayed / Incidence not known
    pancreatitis / Delayed / Incidence not known

    Moderate

    hypophosphatemia / Delayed / 1.3-2.5
    elevated hepatic enzymes / Delayed / Incidence not known
    osteomalacia / Delayed / Incidence not known
    bone pain / Delayed / Incidence not known
    myopathy / Delayed / Incidence not known
    hepatomegaly / Delayed / Incidence not known
    steatosis / Delayed / Incidence not known
    antimicrobial resistance / Delayed / Incidence not known

    Mild

    asthenia / Delayed / 13.0-13.0
    abdominal pain / Early / 9.0-9.0
    headache / Early / 9.0-9.0
    nausea / Early / 5.0-5.0
    flatulence / Early / 4.0-4.0
    dyspepsia / Early / 3.0-3.0
    diarrhea / Early / 3.0-3.0
    vomiting / Early / Incidence not known
    pruritus / Rapid / Incidence not known
    rash / Early / Incidence not known

    DRUG INTERACTIONS

    Abacavir: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Abacavir; Dolutegravir; Lamivudine: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Abacavir; Lamivudine, 3TC: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Abacavir; Lamivudine, 3TC; Zidovudine, ZDV: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Alogliptin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Amiloride: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion. Coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as amiloride, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or amiloride. Coadministration of these drugs has not been studied, but caution is warranted.
    Amiloride; Hydrochlorothiazide, HCTZ: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion. Coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as amiloride, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or amiloride. Coadministration of these drugs has not been studied, but caution is warranted.
    Aminoglycosides: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as aminoglycosides, may increase the risk of developing nephrotoxicity, even in patients who have normal renal function.
    Bictegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Cabozantinib: (Minor) Monitor for an increase in cabozantinib-related adverse reactions if coadministration with adefovir is necessary. Cabozantinib is a Multidrug Resistance Protein 2 (MRP2) substrate and adefovir is an MRP2 inhibitor. MRP2 inhibitors have the potential to increase plasma concentrations of cabozantinib; however, the clinical relevance of this interaction is unknown.
    Canagliflozin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Celecoxib: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Cidofovir: (Severe) The administration of cidofovir with another potentially nephrotoxic agent, such as adefovir, is contraindicated. Adefovir should be discontinued at least 7 days prior to beginning cidofovir.
    Cimetidine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as cimetidine, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or cimetidine. Coadministration of these drugs has not been studied, but caution is warranted.
    Clofarabine: (Moderate) Concomitant use of clofarabine and adefovir may result in altered clofarabine levels because both agents are substrates of OAT1. Therefore, monitor for signs of clofarabine toxicity such as gastrointestinal toxicity (e.g., nausea, vomiting, diarrhea, mucosal inflammation), hematologic toxicity, and skin toxicity (e.g. hand and foot syndrome, rash, pruritus) in patients also receiving OAT1 substrates.
    Cyclosporine: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as cyclosporine, may increase the risk of developing nephrotoxicity, even in patients who have normal renal function. Cyclosporine itself can cause structural kidney damage. Monitor renal function and fluid status carefully during co-use.
    Dapagliflozin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Dextromethorphan; Quinidine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as quinidine, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Dichlorphenamide: (Major) Use of dichlorphenamide and adefovir is not recommended because of increased adefovir exposure and a risk of adefovir-related adverse effects. Monitor closely for signs of drug toxicity if coadministration cannot be avoided. For example, it is important to monitor renal function for all patients during treatment with adefovir, as the drug may cause nephrotoxicity. Increased adefovir exposure is possible. Adefovir is a sensitive OAT1 substrate. Dichlorphenamide inhibits OAT1.
    Diclofenac: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Diclofenac; Misoprostol: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Didanosine, ddI: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Diflunisal: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Digoxin: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as digoxin, may decrease adefovir elimination by competing for common renal tubular transport systems; therefore increasing serum concentrations of either adefovir and/or digoxin may occur. Coadministration of these drugs has not been studied, but caution is warranted.
    Diphenhydramine; Ibuprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Diphenhydramine; Naproxen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Dofetilide: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as dofetilide, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Dolutegravir; Lamivudine: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Dolutegravir; Rilpivirine: (Major) Patients who are concurrently taking adefovir (a nucleotide analog) with antiretrovirals (i.e., anti-retroviral non-nucleoside reverse transcriptase inhibitors (NNRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Donepezil; Memantine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as memantine, may decrease adefovir elimination by competing for common renal tubular transport systems; therefore increasing serum concentrations of either adefovir and/or memantine may occur.
    Doravirine; Lamivudine; Tenofovir disoproxil fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Efavirenz; Emtricitabine; Tenofovir: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Efavirenz; Lamivudine; Tenofovir Disoproxil Fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Empagliflozin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine: (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Emtricitabine; Rilpivirine; Tenofovir alafenamide: (Major) Patients who are concurrently taking adefovir (a nucleotide analog) with antiretrovirals (i.e., anti-retroviral non-nucleoside reverse transcriptase inhibitors (NNRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations). (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Emtricitabine; Rilpivirine; Tenofovir disoproxil fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Major) Patients who are concurrently taking adefovir (a nucleotide analog) with antiretrovirals (i.e., anti-retroviral non-nucleoside reverse transcriptase inhibitors (NNRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations). (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Emtricitabine; Tenofovir alafenamide: (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Emtricitabine; Tenofovir disoproxil fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Moderate) Patients who are concurrently taking adefovir with emtricitabine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Entecavir: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations). Additionally, while both entecavir and adefovir are eliminated by active tubular secretion, per the manufacturer of entecavir, neither the pharmacokinetics of entecavir nor adefovir were altered when given concomitantly.
    Ertugliflozin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Esomeprazole; Naproxen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Etodolac: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Famotidine; Ibuprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Fenoprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Flurbiprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Food: (Moderate) The pharmacokinetic parameters of anti-retroviral medications (anti-retroviral non-nucleoside reverse transcriptase inhibitors (NNRTIs), anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs), anti-retroviral nucleotide reverse transcriptase inhibitors, and anti-retroviral protease inhibitors) metabolized through the CYP isoenzyme system are slightly altered by smoked and oral marijuana. Despite this interaction, marijuana is not expected to adversely affect anti-retroviral efficacy.However, the incidence of marijuana associated adverse effects may change following coadministration with anti-retroviral drugs. Many anti-retrovirals are inhibitors of CYP3A4, an isoenzyme partially responsible for the metabolism of marijuana's most psychoactive compound, delta-9-tetrahydrocannabinol (Delta-9-THC). When given concurrently with anti-retrovirals, the amount of Delta-9-THC converted to the active metabolite 11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC) may be reduced. These changes in Delta-9-THC and 11-OH-THC plasma concentrations may result in an altered marijuana adverse event profile.
    Gallium Ga 68 Dotatate: (Major) Avoid use of mannitol and adefovir, if possible. Concomitant administration of nephrotoxic drugs, such as adefovir, increases the risk of renal failure after administration of mannitol.
    Glipizide; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Glyburide; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Hyaluronidase, Recombinant; Immune Globulin: (Moderate) Immune Globulin (IG) products have been reported to be associated with renal dysfunction, acute renal failure, osmotic nephrosis, and death. Patients predisposed to acute renal failure include patients receiving known nephrotoxic drugs like adefovir. Coadminister IG products at the minimum concentration available and the minimum rate of infusion practicable. Also, closely monitor renal function.
    Hydrochlorothiazide, HCTZ; Triamterene: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as triamterene, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or triamterene.
    Hydrocodone; Ibuprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Ibuprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Ibuprofen; Oxycodone: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Ibuprofen; Pseudoephedrine: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Immune Globulin IV, IVIG, IGIV: (Moderate) Immune Globulin (IG) products have been reported to be associated with renal dysfunction, acute renal failure, osmotic nephrosis, and death. Patients predisposed to acute renal failure include patients receiving known nephrotoxic drugs like adefovir. Coadminister IG products at the minimum concentration available and the minimum rate of infusion practicable. Also, closely monitor renal function.
    Indomethacin: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Inotersen: (Moderate) Use caution with concomitant use of inotersen and adefovir due to the risk of glomerulonephritis and nephrotoxicity.
    Ketoprofen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Ketorolac: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Lamivudine, 3TC: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Lamivudine, 3TC; Zidovudine, ZDV: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Lamivudine; Tenofovir Disoproxil Fumarate: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein. (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Lansoprazole; Naproxen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Linagliptin; Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Mannitol: (Major) Avoid use of mannitol and adefovir, if possible. Concomitant administration of nephrotoxic drugs, such as adefovir, increases the risk of renal failure after administration of mannitol.
    Maraviroc: (Moderate) Use caution and closely monitor for increased adverse effects during concurrent administration of maraviroc and adefovir as increased maraviroc concentrations may occur. Maraviroc is a substrate of multidrug resistance-associated protein (MRP2); adefovir is an inhibitor of MRP2. The effects of this transporter on the concentrations of maraviroc are unknown, although an increase in concentrations and thus, toxicity, are possible.
    Meclofenamate Sodium: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Mefenamic Acid: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Meloxicam: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Memantine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as memantine, may decrease adefovir elimination by competing for common renal tubular transport systems; therefore increasing serum concentrations of either adefovir and/or memantine may occur.
    Metformin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Metformin; Pioglitazone: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Metformin; Repaglinide: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Metformin; Rosiglitazone: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Metformin; Saxagliptin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Metformin; Sitagliptin: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Midodrine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as midodrine, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or midodrine. Coadministration of these drugs has not been studied, but caution is warranted.
    Morphine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as morphine, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Morphine; Naltrexone: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as morphine, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Nabumetone: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Naproxen: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Naproxen; Pseudoephedrine: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Naproxen; Sumatriptan: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Nitisinone: (Moderate) Monitor for increased adefovir-related adverse effects if coadministered with nitisinone. Increased adefovir exposure is possible. Nitisinone inhibits OAT1. Adefovir is an OAT1 substrate.
    Non-nucleoside reverse transcriptase inhibitors: (Major) Patients who are concurrently taking adefovir with non-nucleoside reverse transcriptase inhibitors are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Nonsteroidal antiinflammatory drugs: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Oxaprozin: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Piroxicam: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Procainamide: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as procainamide, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Protease inhibitors: (Major) Patients who are concurrently taking adefovir with antiretrovirals like the protease inhibitors, are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Quinidine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as quinidine, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or these coadministered drugs.
    Quinine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as quinine, may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or quinine.
    Ranitidine: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir with drugs that reduce renal function or compete for active tubular secretion, such as ranitidine may decrease adefovir elimination by competing for common renal tubular transport systems; therefore increasing serum concentrations of either adefovir and/or ranitidine may occur.
    Rilpivirine: (Major) Patients who are concurrently taking adefovir (a nucleotide analog) with antiretrovirals (i.e., anti-retroviral non-nucleoside reverse transcriptase inhibitors (NNRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Rofecoxib: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Stavudine, d4T: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Sulindac: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Tacrolimus: (Moderate) Tacrolimus, in the absence of overt renal impairment, may adversely affect renal function. Care should be taken in using tacrolimus with other nephrotoxic drugs, including adefovir. Assessment of renal function in patients who have received tacrolimus is recommended, as the tacrolimus dosage may need to be reduced.
    Telavancin: (Moderate) Concurrent or sequential use of telavancin with other potentially nephrotoxic drugs such as adefovir may lead to additive nephrotoxicity. Closely monitor renal function and adjust telavancin doses based on calculated creatinine clearance.
    Telbivudine: (Major) Patients who are concurrently taking adefovir with telbivudine are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Tenofovir Alafenamide: (Major) Avoid coadministration of tenofovir alafenamide with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein.
    Tenofovir, PMPA: (Major) Avoid coadministration of tenofovir disoproxil fumarate with adefovir. Both tenofovir and adefovir are primarily excreted via the kidneys by a combination of glomerular filtration and active tubular secretion. Concurrent administration may increase concentrations of both drugs resulting in additive nephrotoxicity. Additionally, in the treatment of chronic hepatitis B, tenofovir should not be administered in combination with adefovir to avoid multi-drug resistance. If coadministration is necessary, patients should be carefully monitored for changes in serum creatinine and phosphorus, and urine glucose and protein.
    Tolmetin: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Triamterene: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as triamterene, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or triamterene.
    Trospium: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion like trospium may decrease adefovir elimination by competing for common renal tubular transport systems, therefore increasing serum concentrations of either adefovir and/or trospium. Monitor for side effects of either drug and monitor renal function. For trospium, monitor for dry mouth, constipation or other anticholinergic effects.
    Valdecoxib: (Moderate) Chronic coadministration of adefovir with nephrotoxic drugs, such as nonsteroidal antiinflammatory drugs may increase the risk of developing nephrotoxicity even in patients who have normal renal function. The use of adefovir with NSAIDs may be done cautiously. As stated in the current adefovir prescribing information, 'Ibuprofen (800 mg PO three times daily), when given concomitantly with adefovir dipivoxil, increased the adefovir Cmax by 33% and AUC by 23%, as well as urinary recovery. The increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.' In an in vitro investigation, the antiviral effect of adefovir was unaltered and the renal proximal tubule accumulation of adefovir was inhibited by the presence of a NSAID. Adefovir is efficiently transported by the human renal organic anion transporter 1, and the presence of this transporter appears to mediate the accumulation of the drug in renal proximal tubules. The in vitro study suggests that the use of a NSAID with adefovir may potentially reduce the nephrotoxic potential of adefovir. Of course, NSAIDs are associated with nephrotoxicity of their own; therefore, further data on the interaction between NSAIDs and adefovir in humans are needed.
    Vancomycin: (Moderate) Adefovir is eliminated renally by a combination of glomerular filtration and active tubular secretion; coadministration of adefovir dipivoxil with drugs that reduce renal function or compete for active tubular secretion, such as parenteral vancomycin, may decrease adefovir elimination by competing for common renal tubular transport systems, thereby increasing serum concentrations of adefovir and/or vancomycin. Additionally, chronic coadministration of adefovir with nephrotoxic drugs, such as vancomycin, may increase the risk of developing nephrotoxicity, even in patients who have normal renal function. Renal function should be monitored closely and vancomycin doses should be adjusted according to vancomycin serum concentrations.
    Zalcitabine, ddC: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).
    Zidovudine, ZDV: (Major) Patients who are concurrently taking adefovir with antiretrovirals (i.e., anti-retroviral nucleoside reverse transcriptase inhibitors (NRTIs)) are at risk of developing lactic acidosis and severe hepatomegaly with steatosis. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals. A majority of these cases have been in women; obesity and prolonged nucleoside exposure may also be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for hepatic disease; however, cases have also been reported in patients with no known risk factors. Suspend adefovir in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

    PREGNANCY AND LACTATION

    Pregnancy

    Adequate and well-controlled studies have not been conducted regarding the use of adefovir during human pregnancy; and prospective data from the Antiretroviral Pregnancy Registry (APR) are insufficient to adequately assess the risk of birth defects, miscarriages, or adverse maternal or fetal outcomes. Reproductive studies in rats and rabbits have shown no embryotoxicity or teratogenicity when given orally at systemic doses greater than 20-times the normal human dose. However, embryotoxicity and fetal malformations were observed in the offspring of rats who were administered intravenous doses greater that 35-times the normal human dose. Because animal reproduction studies are not always predictive of human response, adefovir should be used during pregnancy only if clearly needed and after careful consideration of the risks and benefits. To monitor fetal outcomes of pregnant women exposed to adefovir, a pregnancy registry has been established. It is strongly recommended that health care providers who are treating pregnant women and their newborns report cases of prenatal exposure to adefovir to the Antiretroviral Pregnancy Registry by calling 1-800-258-4263.[27468] There are no data on the effect of adefovir on the transmission of HBV from mother to infant during labor and obstetric delivery; therefore, appropriate immunizations against HBV should be used to prevent neonatal acquisition of hepatitis B virus after birth, in accordance with current guidelines.[28784]

    It is not known whether adefovir is excreted in human breast milk, affects milk production, or has an adverse effect on breast-fed infants. Antiviral medications whose passage into human breast milk have been evaluated include tenofovir and lamivudine. Healthcare providers have not reached a consensus regarding breast-feeding and treatment of HBV infections. In a survey of 226 physicians, 30.5% would recommend breast-feeding for HBV-infected mothers on antiviral therapy, 44% would not recommend breast-feeding during antiviral therapy, and 25.2% stated they were unsure. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.[28784] [46710] [46680] [46688]

    MECHANISM OF ACTION

    Adefovir dipivoxil is an acyclic nucleotide analog of adenosine monophosphate. It serves as a prodrug that is phosphorylated to the active metabolite adefovir diphosphate by cellular kinases. Adefovir diphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate for incorporation into viral DNA, ultimately resulting in DNA chain termination and inhibition of DNA replication.[27088] [27089] Adefovir may also stimulate natural killer cells and immune responsiveness through endogenous interferon-alpha production.[27089] Adefovir is active against the hepatitis B virus, including lamivudine-resistant hepatitis B viruses.

    PHARMACOKINETICS

    Adefovir dipivoxil is administered orally and is rapidly converted to adefovir. In vitro binding of adefovir to plasma or serum proteins is less than 4%, and the volume of distribution ranges from approximately 350 to 400 mL/kg. Adefovir is renally excreted by a combination of glomerular filtration and active tubular secretion, with 45% of the dose recovered as adefovir in the urine over 24 hours at steady state. Plasma adefovir concentrations decline in a biexponential manner with a terminal elimination half-life of 7.5 +/- 1.7 hours.[28784]
     
    Affected cytochrome P450 isoenzymes: None

    Oral Route

    The approximate oral bioavailability of adefovir is 59%; absorption is unaffected when taken with food. After oral administration in chronic hepatitis B patients, the peak adefovir plasma concentration (Cmax) is 18.4 +/- 6.3 ng/mL and occurs between 0.58 to 4 hours (median 1.75 hours) after the dose is administered. Adefovir's area under the plasma concentration-time curve (AUC) is 220 +/- 70 ng x hour/mL.