Tenofovir is primarily used in the treatment of HIV and chronic hepatitis B infections. It works by inhibiting the reverse transcriptase enzyme, which is crucial for the replication of these viruses. In HIV management, it is often combined with other antiretroviral agents as part of a highly active antiretroviral therapy (HAART) regimen to reduce viral load and improve immune function. For hepatitis B, it helps in suppressing viral replication, thereby reducing liver damage and the risk of complications like cirrhosis and liver cancer. Additionally, Tenofovir is used in pre-exposure prophylaxis (PrEP) to prevent HIV infection in high-risk individuals. Its effectiveness and relatively low side effect profile make it a cornerstone in antiviral therapy.