Entecavir is a medication used in the treatment of chronic hepatitis B virus (HBV) infection. It belongs to a class of drugs known as nucleoside analog reverse transcriptase inhibitors.

Chronic hepatitis B is a long-term viral infection that affects the liver, leading to inflammation and potentially serious complications such as cirrhosis and liver cancer. Entecavir works by inhibiting the activity of HBV reverse transcriptase, an enzyme necessary for the replication of the hepatitis B virus. By blocking viral replication, entecavir helps to reduce the viral load in the body and slow down the progression of liver damage