Entavir 0.5mg is an antiviral medication. Entecavir prevents certain virus cells from multiplying in your body Entecavir is used to treat chronic hepatitis B virus (HBV) in adults and children who are at least 2 years old. Entecavir is not a cure for hepatitis. It is not known whether this medicine will prevent cirrhosis or liver cancer. Entecavir may also be used for other purposes not listed in this medication guide.