The non-nucleoside reverse transcriptase inhibitors (NNRTIs),efavirenz (EFV) and nevirapine (NVP),which inhibit HIV replication in host cells by affecting the function of HIV reverse transcriptase,were developed between 1996 and 1998.The compounds bind directly to the reverse transcriptase enzyme,thereby preventing nucleosides from binding to the active sites of the protein and stopping the enzyme from transcribing viral RNA into viral DNA.The efficacy and safety of the drugs have been well documented through a large number of randomized studies in large population groups.