Entecavir is primarily used in the treatment of chronic hepatitis B virus (HBV) infection. It works by inhibiting the replication of the virus, helping to reduce the viral load in the body. This medication is particularly effective in patients with evidence of active viral replication and liver inflammation. By controlling the virus, Entecavir helps to slow down the progression of liver damage, reducing the risk of complications such as cirrhosis and liver cancer. It is often prescribed for long-term use to maintain viral suppression and improve liver function. Entecavir is typically administered orally and is considered a first-line treatment option due to its potency and low resistance profile. Regular monitoring of liver function and viral load is essential during treatment to assess its effectiveness and make necessary adjustments.