Twenty years after its original discovery, tenofovir has acquired a crucial 
position in the fight against human immunodeficiency virus (HIV). First, 
tenofovir disoproxil fumarate (TDF) is not only efficacious against, and has 
been licensed for the treatment of HIV (AIDS), but also HBV (hepatitis B). 
Second, for the treatment of HIV infections, TDF can be used in combination with 
other anti-HIV drugs, such as emtricitabine (combination termed Truvada(®)) and 
Truvada can be further combined with efavirenz, rilpivirine, elvitegravir, 
atazanavir, or darunavir, as a single once-daily oral pill. Third, Truvada can 
be used prophylactically to prevent transmission of HIV infection. And fourth, 
to prevent sexual HIV transmission, tenofovir could also be used topically 
(i.e., as a vaginal gel).