Efavirenz was approved for use in 1998 in the US. Efavirenz belongs to the group of non-nucleotide reverse transcriptase inhibitors. After the HIV virus enters the host cell, the HIV RNA strand is released, and the single strand RNA is reverse transcribed to form DNA by reverse transcriptase. Reverse transcriptase inhibitors, which prevent viral RNA from being copied into DNA, prevent HIV from replicating.