The combination of emtricitabine and tenofovir (Descovy, Truvada) is used along with other medications to treat HIV in adults and children who weigh at least 37 pounds (17 kg). Emtricitabine and tenofovir (Truvada) is also used along with practicing safer sex (e.g., condom use) to reduce the risk of HIV infection) in high-risk adults and teenagers who weigh at least 77 pounds (35 kg). Emtricitabine and tenofovir are in a class of medications called nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs). They work by slowing the spread of HIV in the body. Although emtricitabine and tenofovir will not cure HIV, these medications may decrease your chance of developing acquired immunodeficiency syndrome (AIDS) and HIV-related illnesses such as serious infections or cancer. Taking these medications along with practicing safer sex and making other lifestyle changes may decrease the risk of getting or transmitting the HIV virus to other people.