Used primarily in the treatment of HIV and chronic hepatitis B infections. It works by inhibiting the reverse transcriptase enzyme, which is crucial for viral replication. Administered orally, it is often part of combination antiretroviral therapy to enhance efficacy and reduce the risk of drug resistance. Additionally, it is employed in pre-exposure prophylaxis (PrEP) to prevent HIV infection in high-risk populations. Its dimer form improves bioavailability and stability, making it more effective in clinical settings.