Entecavir, is an antiviral medication used in the treatment of hepatitis B virus infection.In those with both HIV/AIDS and hepatitis B virus antiretroviral medication should also be used. Entecavir is taken by mouth as a tablet or solution.

Common side effects include headache, nausea, high blood sugar, and decreased kidney function. Severe side effects include enlargement of the liver, high blood lactate levels, and liver inflammation if the medication is stopped.While there appears to be no harm from use during pregnancy, this use has not been well studied.Entecavir is in the nucleoside reverse transcriptase inhibitors (NRTIs) family of medications.It prevents the hepatitis B virus from multiplying by blocking reverse transcriptase.

Entecavir was approved for medical use in 2005. It is on the World Health Organization's List of Essential Medicines.^[7] It is available as a generic medication.