Tenofovir is an antiviral medication primarily used to treat HIV and hepatitis B. It works by inhibiting the reverse transcriptase enzyme, which is essential for the replication of these viruses. By blocking this enzyme, Tenofovir helps reduce the viral load in the body, allowing the immune system to function more effectively. Tenofovir is available in different formulations, including Tenofovir disoproxil fumarate (TDF) and Tenofovir alafenamide (TAF). TDF is often used in combination with other antiretroviral drugs, while TAF is a newer formulation that may have fewer side effects on the kidneys and bones. Regular monitoring is recommended for patients on Tenofovir.