Antiva10 mg

Antiva is indicated for the treatment of chronic hepatitis B (CHB) in adults and adolescents 12 years of age and older who have evidence of active viral replication together with either persistently elevated serum aminotransferase levels (ALT or AST) or histologically active liver disease.

Evidence-based classification

• Established/FDA-approved use: Chronic hepatitis B infection with evidence of active viral replication and ongoing liver inflammation, in patients aged 12 years and above.
• Guideline-supported/alternative use: As an alternative nucleos(t)ide analogue for chronic hepatitis B when preferred first-line agents (e.g., tenofovir, entecavir) are unavailable or not tolerated; current hepatology guidelines generally favor newer agents with a higher barrier to resistance as first-line therapy, reserving Antiva for select situations.
• Not an indication: Antiva is not approved for HIV infection and must not be used as HIV therapy; using it in HIV/HBV-coinfected patients without a fully suppressive antiretroviral regimen risks selection of HIV resistance (see Precautions and Warnings).

Each Adefovir Dipivoxil tablet contains Adefovir Dipivoxil INN 10 mg as the active ingredient, along with standard pharmaceutical excipients for oral tablet formulation.

Antiva is an oral prodrug of adefovir, a nucleotide analogue of adenosine monophosphate. It belongs to the class of nucleotide reverse transcriptase inhibitors (NtRTIs) and is used for long-term suppression of hepatitis B virus (HBV) replication in patients with chronic hepatitis B. Following oral administration, Antiva is rapidly converted to adefovir, which is subsequently phosphorylated intracellularly to its active diphosphate metabolite.

Antiva belongs to the therapeutic class of antiviral agents, specifically the nucleotide analogue reverse transcriptase inhibitors (NtRTIs) used in the management of chronic hepatitis B infection.

Adefovir Dipivoxil is a diester prodrug of adefovir. After absorption, it is hydrolyzed to adefovir, which is then phosphorylated by cellular kinases to adefovir diphosphate, the pharmacologically active metabolite.

Adefovir diphosphate inhibits hepatitis B virus (HBV) DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate (dATP) and, after incorporation into viral DNA, causes DNA chain termination. This suppresses HBV replication, leading to reductions in serum HBV DNA levels and, in many patients, normalization of serum aminotransferases and improvement in liver histology.

Adefovir Dipivoxil is administered orally once daily; peak plasma concentrations of adefovir are reached within 0.5 to 4 hours. It is eliminated primarily by the kidneys through a combination of glomerular filtration and active tubular secretion, which is the basis for dose adjustment in renal impairment (see Dosage and Administration).

Antiva tablets should be swallowed whole with water, taken at approximately the same time each day, with or without food. Doses should not be skipped, doubled, or stopped without medical advice.

Antiva has clinically important interactions with the following:

• Tenofovir-containing products (e.g., regimens such as Viread, Truvada, Atripla): Concurrent use with Antiva is not recommended because both are renally eliminated adefovir/tenofovir-type nucleotide analogues, and coadministration provides no additional efficacy benefit while increasing the risk of additive nephrotoxicity.
• Other nephrotoxic drugs (e.g., chronic NSAID use, aminoglycosides, vancomycin, amphotericin B, cyclosporine, tacrolimus): Coadministration with Antiva may increase serum concentrations of adefovir and/or the interacting drug and raises the risk of nephrotoxicity; renal function should be monitored closely if such combinations cannot be avoided.
• Drugs affecting renal tubular secretion: Agents that reduce renal function or compete for active tubular secretion may increase concentrations of adefovir or the co-administered drug.

Inform your physician of all medicines being taken, including over-the-counter drugs and herbal products, before starting Antiva.

The most commonly reported adverse effects with Antiva (occurring in approximately 3% or more of patients) include:

• Asthenia (weakness)
• Headache
• Abdominal pain
• Nausea
• Flatulence
• Diarrhea
• Dyspepsia (indigestion)
• Increased serum creatinine
• Hypophosphatemia (low blood phosphate)

Less common but serious adverse effects include renal impairment or failure, Fanconi syndrome, proximal renal tubulopathy, muscle weakness/myopathy, osteomalacia (bone softening related to proximal tubulopathy), and pancreatitis. Rare, potentially life-threatening reactions — lactic acidosis with severe hepatomegaly and steatosis, and severe exacerbation of hepatitis B after stopping treatment — are discussed further under Precautions and Warnings.

Seek prompt medical attention for unusual muscle pain/weakness, unexplained weight loss, severe abdominal pain, dark urine, or yellowing of the skin/eyes while taking Antiva.

Pregnancy: Antiva is classified as pregnancy category C. There are no adequate and well-controlled studies in pregnant women. Antiva should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus, and only after consultation with a physician. Because stopping antiviral therapy can trigger hepatitis flares, pregnant patients should discuss hepatitis B management carefully with their physician rather than discontinuing treatment on their own.

Lactation: It is not known whether adefovir is excreted in human breast milk. Because many drugs are excreted in human milk and because of the potential for adverse effects in the nursing infant, a decision should be made whether to discontinue nursing or discontinue Antiva, taking into account the importance of the drug to the mother, in consultation with a physician.

Antiva carries several important warnings that require close medical supervision:

• Severe acute exacerbation of hepatitis B after discontinuation: Severe, sometimes fatal, flares of hepatitis B have occurred in patients who discontinued anti-hepatitis B therapy, including Antiva. Liver function should be monitored closely, both clinically and with laboratory tests, for at least several months after stopping treatment. Do not discontinue Antiva without your physician's guidance.
• Nephrotoxicity: Chronic use of Antiva may cause a dose-related risk of kidney toxicity. This risk is higher in patients with pre-existing renal impairment and in those taking other nephrotoxic drugs. Renal function (serum creatinine, phosphate) should be assessed before starting therapy and monitored periodically thereafter; dose adjustment is required in renal impairment (see Dosage and Administration).
• Risk of HIV resistance in unrecognized/untreated HIV infection: Because Antiva has activity against HIV at higher doses, its use in patients with chronic hepatitis B who have unrecognized or untreated HIV infection can lead to the emergence of HIV resistance to certain antiretroviral drug classes. HIV status should be established before starting Antiva.
• Lactic acidosis and severe hepatomegaly with steatosis: Rare but potentially fatal cases have been reported with nucleoside/nucleotide analogues, including Antiva, more frequently at doses higher than the approved dose. Treatment should be suspended if clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity develop.

Antiva should be used with caution in patients with underlying kidney disease and in those receiving concomitant nephrotoxic medications. Regular laboratory monitoring throughout treatment is essential.

Limited data are available on overdose with Antiva; doses higher than the recommended dose have been associated with gastrointestinal symptoms. In case of suspected overdose with Antiva, seek immediate medical attention or contact a poison control center/emergency services. Management is supportive; adefovir can be removed by hemodialysis, and hydration status and renal function should be monitored closely. Do not attempt to manage a suspected overdose at home.

Store Antiva at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Renal impairment: Dose adjustment of Antiva is required based on creatinine clearance (see Dosage and Administration); renal function should be monitored closely, especially in patients with pre-existing kidney disease.

Hepatic impairment: No dose adjustment is required for patients with hepatic impairment; however, these patients require close monitoring given the underlying liver disease being treated.

Elderly: Clinical studies did not include sufficient numbers of patients aged 65 and over; because elderly patients are more likely to have decreased renal function, caution and renal monitoring are advised when using Antiva in this group.

HIV/HBV coinfection: HIV status should be established before starting Antiva due to the risk of HIV resistance (see Precautions and Warnings).

See Pediatric Uses and Pregnancy and Lactation for further population-specific guidance.

The optimal duration of treatment with Antiva for chronic hepatitis B has not been definitively established. Treatment is generally continued long-term to maintain suppression of viral replication, with the specific endpoint (e.g., HBeAg seroconversion, a defined consolidation period after seroconversion, or indefinite therapy in patients with cirrhosis) determined by the treating physician based on virologic, biochemical, and serologic response. Antiva should never be stopped abruptly without medical supervision, as severe hepatitis flares can occur after discontinuation (see Precautions and Warnings).

Adefovir Dipivoxil belongs to the drug class of antiviral agents — specifically, nucleotide analogue reverse transcriptase inhibitors (NtRTIs) used against hepatitis B virus.

Adefovir Dipivoxil is an orally bioavailable diester prodrug of adefovir. After absorption, it is converted to adefovir, which is then phosphorylated by cellular enzymes to the active metabolite adefovir diphosphate. This metabolite competitively inhibits hepatitis B virus (HBV) DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate, and once incorporated into the growing viral DNA chain, causes DNA chain termination, thereby suppressing HBV replication.

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The safety and efficacy of Antiva have been established in adolescents 12 to 17 years of age with chronic hepatitis B and evidence of active viral replication and liver disease, at the same 10 mg once-daily dose used in adults.

Antiva is not recommended for use in children younger than 12 years, as safety and efficacy have not been established in this age group. No dosing recommendation is available for pediatric patients with renal impairment.