Used to treat chronic hepatitis B virus (HBV) infection in adults and children. It works by reducing the amount of the virus in the body, helping to improve liver function and reduce the risk of liver damage, cirrhosis, and liver cancer. It is not a cure for HBV but helps control the infection and may slow disease progression. Typically prescribed for patients with active viral replication and evidence of liver inflammation. Must be taken regularly as directed, since inconsistent use can lead to drug resistance. Not effective against hepatitis C or HIV.