entecavir

Entecavir is an antiviral medication used in the treatment of chronic hepatitis B virus (HBV) infection. It is a nucleoside analogue of guanosine and is active against HBV replication. Entecavir is typically administered by mouth and is available in tablet form, with dosing adapted to age and renal function.

Mechanism of action

Entecavir inhibits HBV DNA polymerase, an enzyme essential for viral DNA replication. By competitively inhibiting the enzyme and causing chain termination, it reduces HBV DNA levels and helps normalize liver enzymes. It has a relatively high barrier to the development of antiviral resistance compared with some other HBV therapies.

Clinical uses

Entecavir is approved for the treatment of chronic hepatitis B in adults and in certain pediatric patients. It is used in nucleoside-naive patients and in those with prior nucleoside resistance, including lamivudine resistance. The goal of therapy is sustained suppression of HBV DNA, biochemical response (normalization of ALT), and improvement of liver histology.

Efficacy and safety

Clinical studies have shown entecavir to rapidly suppress HBV DNA in many patients, with ongoing treatment needed to maintain response. Common adverse effects include headache, fatigue, dizziness, and gastrointestinal symptoms. Serious but rare risks include lactic acidosis and severe hepatomegaly with steatosis, particularly in patients with advanced liver disease. Entecavir requires dose adjustment in renal impairment and should be used with caution in decompensated cirrhosis. It is generally avoided in pregnancy unless clearly needed.

Dosing and availability

In adults, typical regimens involve once-daily dosing, with pediatric dosing based on body weight or age. Entecavir is available by prescription and is marketed under brand names such as Baraclude.