Oral Drug Approved for Chronic Hepatitis B
Adefovir dipivoxil is a prodrug of adefovir, a nucleotide analogue that blocks the replication of hepatitis B virus. The antiviral agent slows the progression of chronic hepatitis B but has not yet been shown to cure the disease. FDA made its decision primarily on the basis of two studies in which the patients took adefovir dipivoxil or a placebo for 48 weeks.
Up to 25 percent of participants in the studies had a severe, acute exacerbation of hepatitis after stopping treatment with the drug. Patients' liver function should be monitored after discontinuation of the therapy, according to the product's labeling.
The adverse events most commonly observed during the studies were muscle weakness, headache, abdominal pain, nausea, flatulence, diarrhea, and dyspepsia, which occurred at similar rates in the adefovir dipivoxil and placebo groups.
According to the product's labeling, patients without renal impairment should take 10 mg of adefovir dipivoxil once daily without regard to food. Doses should be taken less frequently by patients with a creatinine clearance of 1049 mL/min and those undergoing hemodialysis. There is no information on the appropriate dosage for patients with a creatinine clearance of less than 10 mL/min who are not undergoing hemodialysis.
Hepsera is available in 10-mg tablets. Gilead announced that the wholesaler acquisition cost for a 30-count bottle of the product is $440. The company has set up a patient assistance program, reachable at 800-GILEAD-5 or 650-574-3000, for patients who do not have insurance or cannot afford to pay for the treatment.