[Treatment of chronic hepatitis B]

Chronic hepatitis B develops in 3 phases: immune tolerance, where viral replication is strong and there is little or no fibrosis; immune activity phase with low viral replication and rapidly developing fibrosis as well as an elevated risk of cirrhosis; low viral replication and remission, with a risk, nonetheless, of reactivation. Antiviral treatment is indicated in patients with moderate or severe levels of either fibrosis or activity (necrotic and inflammatory lesions). Standard interferon treatment produces a prolonged response rate on the order to 20-40%; side effects are frequent but generally mild and reversible when treatment stops. Pegylated interferon (standard interferon conjugated with polyethylene glycol) has substantially better efficacy and comparable tolerance. Lamivudine (a nucleoside analog) has several advantages over interferon: oral administration, excellent tolerance, and rapid antiviral effect. Its principal disadvantage is the frequency of resistant mutations. Adefovir and entecavir have oral administration, are well tolerated and associated with a low incidence of resistance. They induce a sustained response after withdrawal of therapy in only a minority of patients and therefore the treatment needs to be indefinitely administered in the majority of patients.