Lamivudine is an antiviral medication primarily used to treat infections caused by the human immunodeficiency virus (HIV) and the hepatitis B virus (HBV). It works by inhibiting the replication of these viruses, helping to reduce their presence in the body and improve the immune system's function. This medication is often prescribed as part of a combination therapy to enhance its effectiveness. Lamivudine is available in tablet and liquid forms and is typically taken once daily. Like all medications, it may have side effects, so it's important for patients to discuss their health conditions with a healthcare provider before starting treatment.