Safety and Toxicity of Individual Antiretroviral Agents in Pregnancy NUCLEOSIDE AND NUCLEOTIDE ANALOGUE REVERSE TRANSCRIPTASE INHIBITORS

There are currently six approved nucleoside analogue reverse transcriptase inhibitors. Data are available from clinical trials in human pregnancy for zidovudine and lamivudine, while didanosine and stavudine are under study. Zalcitabine and abacavir have not been studied in pregnant women. Tenofovir disoproxil fumarate is the first acyclic nucleotide analogue reverse transcriptase inhibitor. The nucleoside analogue drugs require three intracellular phosphorylation steps to form the triphosphate nucleoside, which is the active drug moiety; tenofovir, an acyclic nucleotide analogue drug, contains a mono-phosphate component attached to the adenine base, and hence only requires two phosphorylation steps to form the active moiety.