Tenofovir disoproxil fumarate. Molecular model of the drug tenofovir disoproxil fumarate (C19.H30.N5.O10.?C4.H4.O4). This antiretroviral medication, sold under the brand name Viread, is used to prevent and treat HIV/AIDS and to treat chronic hepatitis B. The active substance is tenofovir, while tenofovir disoproxil fumarate is a prodrug that is used because of its better absorption in the gut. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue) and oxygen (red).