tenofovir disoproxil is a nucleotide analog reverse-transcriptase inhibitor (ntrti). it selectively inhibits viral reverse transcriptase, a crucial enzyme in retroviruses such as human immunodeficiency virus (hiv), while showing limited inhibition of human enzymes, such as dna polymerases α, β, and mitochondrial dna polymerase γ. in vivo tenofovir disoproxil fumarate is converted to tenofovir, an acyclic analog of deoxyadenosine 5'-monophosphate (d-amp).