zidovudine + zalcitabine + nevirapine

This is a combination antiretroviral regimen comprising **zidovudine**, **zalcitabine**, and **nevirapine**. All three drugs target HIV-1: zidovudine and zalcitabine are *nucleoside reverse transcriptase inhibitors (NRTIs)*, while nevirapine is a *non-nucleoside reverse transcriptase inhibitor (NNRTI)*. NRTIs act by incorporating into viral DNA and causing chain termination during reverse transcription, thereby inhibiting viral replication. NNRTIs, such as nevirapine, bind directly to reverse transcriptase at an allosteric site and block enzyme activity, preventing the conversion of viral RNA to DNA. This combination was designed to provide more potent and durable suppression of HIV-1 compared to monotherapy, particularly in patients with limited prior antiretroviral exposure[7]. Clinical trials demonstrated additive or synergistic antiviral effects, with improved immunological responses and potentially delayed resistance development compared to dual therapy[5][7]. Zidovudine and zalcitabine have been associated with mitochondrial toxicity and peripheral neuropathy[2][5], while nevirapine carries risk of severe hepatotoxicity and dermatologic reactions[4][6]. The use of this triple combination has been largely replaced by regimens with safer and more effective agents, but it reflects the early era of combination HIV therapy.