Entecavir is an oral antiviral drug used in the treatment of hepatitis B infection. Entecavir is a nucleoside analog (more specifically, a guanine analogue) that inhibits reverse transcription, DNA replication and transcription in the viral replication process. Entecavir is more efficacious than previous agents used to treat hepatitis B (lamivudine and adefovir). Entecavir is also indicated for the treatment of chronic hepatitis B in adults with HIV/AIDS infection. However, Entecavir is not active against HIV.