We prepared a hepatotropic conjugate, suitable for intramuscular (IM) injection, of lactosaminated poly-L-lysine with adenine arabinoside monophosphate (ara-AMP), a drug active against hepatitis B virus (HBV). We studied its organ distribution in mice and its antiviral activity in woodchucks that are carriers of woodchuck hepatitis virus (WHV). In mice, after IM administration of a conjugate tritiated in the drug moiety (5.2 micrograms/g equal to 2 micrograms/g of ara-AMP) radioactivity in liver was three times greater than in kidney, spleen, and intestine. On the contrary, after IM injection of unconjugated, tritiated, ara-AMP (5 micrograms/g) the amounts of radioactivity in liver, spleen, and kidney were similar. Unconjugated ara-AMP and the conjugate were administered IM to woodchucks for 13 days. Unconjugated ara-AMP decreased viremia at the daily dose of 5 mg/kg but was ineffective at 2.5 mg/kg. The conjugate at the daily doses of 4.2 and 7 mg/kg (equal to 1.5 and 2.5 mg/kg of ara-AMP, respectively) markedly lowered the viremia, which decreased to undetectable levels in the animals treated with the higher dose. Assuming that in HBV-infected patients the same doses will be active, then the amount of conjugate (soluble at 200 mg/mL) required by a 70-kg patient will be contained in a volume of 1.5 to 2.5 mL, compatible with the IM route. Compared with a similar ara-AMP complex with lactosaminated human albumin, currently being studied in clinical trials for the treatment of chronic type B hepatitis, which must be infused intravenously, the present conjugate might provide more patient compliance because of IM administration.