<prompt> Which one of the following is a nucleoside analog reverse transcriptase inhibitor?EfavirenzNevirapineZidovudineSaquinavir  <response>: C Zidovudine RTIs come in 3 forms: Nucleoside analog reverse transcriptase inhibitors NARTIs or NRTIs Nucleotide analog reverse transcriptase inhibitors NtARTIs or NtRTIs Non-nucleoside reverse transcriptase inhibitors NNRTIs Nucleoside analog reverse transcriptase inhibitors NARTIs or NRTIs: compose the first class of antiretroviral drugs developed. In order to be incorporated into the viral DNA, NRTIs must be activated in the cell by the addition of three phosphate groups to their deoxyribose moiety, to form NRTI triphosphates. This phosphorylation step is carried out by cellular kinase enzymes. Zidovudine, Didanosine, Zalcitabine, Stavudine, Lamivudine, Abacavir, Emtricitabine Nucleotide analog reverse transcriptase inhibitors NtARTIs or NtRTIs: Normally, nucleoside analogs are converted into nucleotide analogs by the body. Taking nucleotide analog reverse transcriptase inhibitors NtARTIs or NtRTIs directly allows conversion steps to be skipped, causing less toxicity. Tenofovir, Adefovir Non-nucleoside reverse transcriptase inhibitors NNRTIs: NNRTIs are the third class of antiretroviral drugs that were developed. This class of drugs was first described at the Rega Institute for Medical Research Belgium: Efavirenz, Nevirapine, Delavirdine, protease inhibitors sequinavir, Indinavir, Ritonavir, Nelfinavir etc., Research have designed molecules which dually inhibit both reverse transcriptase RT and integrase IN. These drugs have been termed Portmanteau inhibitors. 