Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ADEFOVIR DIPIVOXIL vs OFIRMEV
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Adefovir dipivoxil is a prodrug of adefovir, an acyclic nucleotide analog of adenosine monophosphate. It is phosphorylated intracellularly to adefovir diphosphate, which inhibits hepatitis B virus (HBV) DNA polymerase by competing with the natural substrate deoxyadenosine triphosphate and causing DNA chain termination after incorporation into viral DNA.
OFIRMEV (acetaminophen) is a para-aminophenol derivative with analgesic and antipyretic activity. Its mechanism of action is not fully understood, but it is thought to involve inhibition of cyclooxygenase (COX) enzymes in the central nervous system, with minimal peripheral COX inhibition. It may also act on serotonergic pathways and cannabinoid receptors.
Treatment of chronic hepatitis B in adults with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease.,Treatment of chronic hepatitis B in pediatric patients aged 12 years and older.
Management of mild to moderate pain,Management of moderate to severe pain with adjunctive opioid analgesics,Reduction of fever
10 mg orally once daily on an empty stomach.
IV: 1000 mg every 6 hours or 650 mg every 4 hours; maximum single dose: 1000 mg; minimum dosing interval: 4 hours; maximum daily dose: 4000 mg.
Terminal elimination half-life is 7.5 hours (range 5–10 h); clinically, supports once-daily dosing with dose adjustment for renal impairment.
Terminal elimination half-life is 2-3 hours in adults (2.5-3 hours in children). Clinically, dosing every 4-6 hours is needed to maintain therapeutic levels.
Adefovir dipivoxil is rapidly converted to adefovir by esterases. Adefovir is not significantly metabolized; it is eliminated renally by a combination of glomerular filtration and active tubular secretion. No CYP450-mediated metabolism.
Acetaminophen is primarily metabolized in the liver via conjugation with glucuronide (50-60%) and sulfate (20-30%). A minor amount is oxidized by cytochrome P450 (CYP2E1, CYP1A2, CYP3A4) to a toxic reactive metabolite (NAPQI), which is normally detoxified by glutathione. At toxic doses, glutathione is depleted, leading to NAPQI accumulation and hepatotoxicity.
Renal (90% as unchanged drug via active tubular secretion); biliary/fecal (<5%)
Primarily renal (85% as sulfate and glucuronide conjugates, 10% as unchanged drug). Less than 5% fecal/biliary.
≤4% (low binding; negligible affinity for serum proteins)
10-25% bound to albumin at therapeutic concentrations.
0.4 L/kg (392 L in adults); indicates extensive tissue distribution (including liver).
0.8-1.0 L/kg. Indicates distribution into total body water.
Oral: 59% (range 40–70%); prodrug adefovir dipivoxil is rapidly converted to adefovir.
100% (intravenous); not applicable for other routes as OFIRMEV is IV only.
Cr Cl ≥50 m L/min: 10 mg every 24 hours; Cr Cl 30-49 m L/min: 10 mg every 48 hours; Cr Cl 10-29 m L/min: 10 mg every 72 hours; Hemodialysis: 10 mg every 7 days after dialysis.
No dose adjustment required for GFR ≥30 m L/min. For GFR <30 m L/min, extend dosing interval to every 8 hours; maximum daily dose 3000 mg.
No adjustment required for mild-moderate hepatic impairment (Child-Pugh A or B). Not studied in severe (Child-Pugh C).
Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce total daily dose by 50% (max 2000 mg/day). Child-Pugh Class C: Contraindicated or use with extreme caution; reduce dose to 50% of standard and extend interval to every 8 hours; maximum 2000 mg/day.
Approved for age ≥12 years: 10 mg orally once daily. For age <12 years, use is not established.
Weight-based: <10 kg: 7.5 mg/kg/dose every 6 hours; 10-50 kg: 15 mg/kg/dose every 6 hours; >50 kg: 1000 mg every 6 hours or 650 mg every 4 hours. Maximum single dose: 15 mg/kg (up to 1000 mg); maximum daily dose: 75 mg/kg (up to 4000 mg).
Monitor renal function; adjust dose based on Cr Cl. No specific dose adjustment solely for age.
No specific dose adjustment; consider reduced renal function. For Cr Cl <30 m L/min, extend interval to every 8 hours. Maximum daily dose: 3000 mg in frail elderly or with comorbidities.
WARNING: SEVERE ACUTE EXACERBATION OF HEPATITIS B, NEPHROTOXICITY, HIV RESISTANCE, and LACTIC ACIDOSIS/HEPATOMEGALY WITH STEATOSIS. See full prescribing information for complete boxed warning.
Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 mg per day, and often involve more than one acetaminophen-containing product.
Severe acute exacerbation of hepatitis B upon discontinuation of therapy,Nephrotoxicity: monitor renal function, especially in patients at risk or with pre-existing renal impairment,HIV resistance: test for HIV before initiation in patients with unknown HIV status,Lactic acidosis and severe hepatomegaly with steatosis,Use with caution in elderly, renal impairment, or concomitant nephrotoxic agents
Risk of serious hepatotoxicity, especially with doses >4000 mg/day or in patients with underlying liver disease,Risk of severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalized exanthematous pustulosis) – discontinue at first sign of rash,Risk of hypersensitivity reactions including anaphylaxis,Use caution in patients with severe hepatic impairment, active hepatic disease, or alcoholism,Avoid concurrent use of other acetaminophen-containing products
Hypersensitivity to adefovir dipivoxil or any component of the formulation
Known hypersensitivity to acetaminophen or any component of the formulation,Severe hepatic impairment or active liver disease (relative contraindication without black box)
No clinically significant food interactions; can be taken with or without food. Avoid high-fat meals if gastrointestinal intolerance occurs.
No known food interactions. However, avoid excessive alcohol consumption as it may increase the risk of liver damage.
Adefovir dipivoxil is an FDA Pregnancy Category C drug. Animal studies have shown teratogenicity (malformations, embryo-fetal toxicity) at doses 23 times the human therapeutic dose. There are no adequate and well-controlled studies in pregnant women. In first trimester, risk cannot be excluded; use only if benefit outweighs risk. In second and third trimesters, potential for fetal harm exists; consider alternative therapy.
Acetaminophen (OFIRMEV) is generally considered low risk across all trimesters. No increased risk of major congenital anomalies has been consistently demonstrated. Chronic high-dose use in third trimester may be associated with preterm birth or low birth weight. Avoid prolonged use above recommended doses.
It is unknown whether adefovir is excreted in human breast milk. Animal studies indicate it is present in rat milk. The M/P ratio is not established. Given the potential for serious adverse reactions in nursing infants, breastfeeding is not recommended during therapy or for 2 weeks after last dose.
Acetaminophen is excreted in breast milk in low concentrations (M/P ratio approximately 0.9-1.0). Considered compatible with breastfeeding; peak milk levels occur 1-2 hours after maternal dosing. Use lowest effective dose for shortest duration.
Pregnancy may increase renal clearance; however, specific pharmacokinetic data are lacking. Dose adjustment is not routinely recommended but may be necessary if renal function changes. Use standard dose of 10 mg once daily with monitoring of renal function and HBV DNA levels.
No dose adjustment required during pregnancy. Pharmacokinetic changes in pregnancy (increased volume of distribution, clearance) may lead to lower peak concentrations but standard dosing remains effective. Maximum single dose: 1 g; maximum daily dose: 4 g.
Monitor renal function closely; dose adjust for Cr Cl <50 m L/min. Check LFTs and HBV DNA every 3 months. Avoid in decompensated cirrhosis. HIV co-infected patients require concomitant antiretroviral therapy due to risk of HIV resistance. Prolonged therapy may lead to adefovir-resistant HBV mutations (rt A181V/T, rt N236T).
OFIRMEV (acetaminophen) injection is an IV formulation of acetaminophen used for pain and fever management. It is a prodrug that requires no hepatic conversion, providing rapid onset of action. Monitor for hepatotoxicity; maximum daily dose is 4 grams in adults but lower in patients with hepatic impairment or malnutrition. Do not exceed 1 gram per dose. Hypotension and anaphylaxis have been reported. Not interchangeable with oral acetaminophen due to dose equivalency. Use with caution in patients with alcohol use disorder.
Take with or without food at the same time daily.,Do not stop taking without consulting your doctor; stopping may cause severe hepatitis flare.,Report any signs of kidney problems (decreased urination, swelling) or lactic acidosis (unusual muscle pain, trouble breathing).,Regular blood tests are required to monitor liver and kidney function.,Use effective contraception during treatment if you or your partner can become pregnant.,Avoid alcohol and other medications that can damage the liver or kidneys without medical advice.
OFIRMEV is given intravenously for pain or fever.,Do not take additional acetaminophen-containing medications while receiving OFIRMEV.,Report any signs of allergic reaction (rash, itching, swelling, trouble breathing).,Seek immediate medical attention if you experience severe abdominal pain, yellowing of skin or eyes, or dark urine.,Inform your healthcare provider about all medications you are taking, especially blood thinners.
"Coadministration of adefovir dipivoxil and tenofovir disoproxil may reduce the antiviral efficacy of tenofovir by competing for renal tubular secretion via organic anion transporters (OATs) and potentially intracellular phosphorylation pathways. This competition can decrease tenofovir's intracellular active metabolite concentrations, leading to suboptimal viral suppression and increased risk of treatment failure in patients with chronic hepatitis B."
"The serum concentration of Teriflunomide can be increased when it is combined with Adefovir dipivoxil."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ADEFOVIR DIPIVOXIL vs OFIRMEV, answered by our medical review team.
ADEFOVIR DIPIVOXIL is a Antiviral that works by Adefovir dipivoxil is a prodrug of adefovir, an acyclic nucleotide analog of adenosine monophosphate. It is phosphorylated intracellularly to adefovir diphosphate, which inhibits hepatitis B virus (HBV) DNA polymerase by competing with the natural substrate deoxyadenosine triphosphate and causing DNA chain termination after incorporation into viral DNA.. OFIRMEV is a Non-opioid Analgesic that works by OFIRMEV (acetaminophen) is a para-aminophenol derivative with analgesic and antipyretic activity. Its mechanism of action is not fully understood, but it is thought to involve inhibition of cyclooxygenase (COX) enzymes in the central nervous system, with minimal peripheral COX inhibition. It may also act on serotonergic pathways and cannabinoid receptors.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ADEFOVIR DIPIVOXIL and OFIRMEV depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ADEFOVIR DIPIVOXIL is: 10 mg orally once daily on an empty stomach.. The standard adult dose of OFIRMEV is: IV: 1000 mg every 6 hours or 650 mg every 4 hours; maximum single dose: 1000 mg; minimum dosing interval: 4 hours; maximum daily dose: 4000 mg.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ADEFOVIR DIPIVOXIL and OFIRMEV in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ADEFOVIR DIPIVOXIL is classified as Category C. Adefovir dipivoxil is an FDA Pregnancy Category C drug. Animal studies have shown teratogenicity (malformations, embryo-fetal toxicity) at doses 23 times the human therapeutic dose. OFIRMEV is classified as Category C. Acetaminophen (OFIRMEV) is generally considered low risk across all trimesters. No increased risk of major congenital anomalies has been consistently demonstrated. Chronic high-dos. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.