Entecavir is a guanosine nucleoside analogue with potent and selective activity against HBV polymerase. For pharmacological action it is phosphorylated to the active triphosphate (TP) form. Entecavir triphosphate functionally inhibits all 3 activities of the viral polymerase-
Priming of the HBV polymerase,
Reverse transcription of the negative strand from the pregenomic messenger RNA
Synthesis of the positive strand HBV DNA.
Administration of Entecavir with food decreases absorption and so it should be taken in an empty stomach (at least 2 hours before or 2 hours after meal).
Adult over 16 years, not previously treated with nucleoside analogues: 0.5 mg once daily.
Adult over 16 years with lamivudine or telbivudine resistant chronic hepatitis B: 1 mg once daily.