Adefovir dipivoxil is a diester prodrug of adefovir. Adefovir is an acyclic nucleotide analog with activity against human hepatitis B virus (HBV). Adefovir 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 and by causing DNA chain termination after its incorporation into viral DNA. The approximate oral bioavailability of adefovir from a 10 mg single dose is 59%. In vitro binding of adefovir to human plasma or human serum proteins is 4%. Adefovir is excreted through renal route by a combination of glomerular filtration and active tubular secretion.

Adefovir Dipivoxil is indicated for the 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.

The recommended dose of Adefovir in chronic hepatitis B patients with adequate renal function is 10 mg, once daily, taken orally, without regard to food.

Adefovir dipivoxil is contraindicated in patients with previously demonstrated hypersensitivity to any of the components of the product.

The most common side effects of adefovir dipivoxil are weakness, headache, stomach pain and nausea. Severe acute exacerbations of hepatitis have been reported in patients who have discontinued anti-hepatitis B therapy, including therapy with adefovir dipivoxil. In patients at risk of or having underlying renal dysfunction, chronic administration of adefovir dipivoxil may result in nephrotoxicity. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with other antiretrovirals.

Overdose Effects

Doses of adefovir dipivoxil 500 mg daily for 2 weeks and 250 mg daily for 12 weeks have been associated with gastrointestinal side effects. If overdose occurs the patient must be monitored for evidence of toxicity and standard supportive treatment applied as necessary.

Pregnancy & Lactation

Pregnancy Category C. There are no adequate and well-controlled studies in pregnant women. Adefovir dipivoxil should be used during pregnancy only if clearly needed and after careful consideration of the risks and benefits. It is not known whether adefovir is excreted in human milk. Mothers should be instructed not to breast-feed if they are taking adefovir dipivoxil.

Precautions & Warnings

Patients who discontinued adefovir dipivoxil should be monitored at repeated intervals over a period of time for hepatic function. The patients at risk of or having underlying renal dysfunction should be monitored closely for renal function and may require dose adjustment.