Emtricitabine is a cytosine nucleoside analog (Figure 3) that is a competitive inhibitor of human immunodeficiency virus-1 (HIV-1) reverse transcriptase. It is metabolized by cellular kinases-mediated phosphorylation to the triphosphate form. Emtricitabine triphosphate is the active form that blocks the HIV replication by terminating its genetic chain elongation, and thus, it prevents the generation of complementary DNA from the viral RNA and reduces the viral load. The drug was first approved by the U.S. FDA as an orally bioavailable, once-daily antiretroviral drug in 2003. It is now used in combination with other antiretroviral drugs for the treatment of HIV-1 infection [62,63]. Combinations with tenofovir disoproxil fumarate (Truvada), tenofovir alafenamide (Descovy; 2016), rilpivirine, and tenofovir alafenamide (Odefsey; 2016), or bictegravir and tenofovir alafenamide (Biktarvy; 2018) are available.