Efavirenz was approved by the Food and Drug Administration (FDA) on September 21, 1998, making it the 14th approved antiretroviral drug. Efavirenz (brand name sustiva) is an orally active, non-nucleoside reverse transcriptase inhibitor (nnRTI) that is specific for human immunodeficiency virus, type1 (HIV-1). Efavirenz has a terminal half-life of 52–76 hours after a single dose and 40–55 hours after multiple dosing. It is used together with other antiretrovirals to delay the progression of HIV infection. By doing this, your immune system should improve (increase in CD4+ count) and you will be better protected against infections. Efavirenz does not cure AIDS or completely kill the HIV virus, but helps to prevent further damage by slowing down the production of new viruses. Efavirenz was combined with the popular HIV medication Truvada and approved by the FDA in July of 2006, under the brand name Atripla. Efavirenz is the preferred non-nucleoside reverse transcriptase inhibitor for first-line antiretroviral treatment in many countries.