Sustiva (efavirenz) is a non-nucleoside reverse transcriptase inhibitor (NNRTI). Like the other NNRTIs – which include Viramune (nevirapine) and Rescriptor (delavirdine) – Sustiva blocks HIV's reverse transcriptase enzyme, a protein that helps the virus invade the DNA inside human cells. (Click here to learn more about the life cycle of HIV and the ways in which NNRTIs and other HIV drugs work).
An antiretroviral (ARV) drug regimen consisting of Sustiva and two regular nucleoside analogues (e.g., Truvada) is a popular option for HIV-positive people starting therapy for the first time. In recent years, most people starting a Sustiva-based regimen take Atripla. Sustiva only needs to be taken once a day, preferably on an empty stomach, usually at bedtime.
As discussed in the our lesson, "When Should I Start Treatment, and What Should I Take First?", Sustiva is the only NNRTI recommended as a preferred choice by the US Department of Health and Human Services (DHHS)—which sets HIV treatment guidelines—for patients who have never been on ARV therapy before (the others are recommended as "alternative" options) . This is because Sustiva has been shown to be associated with long-term benefits in people who have both low and high (>100,000 copies/mL) viral loads before starting therapy. Other "preferred" first-line options include protease inhibitors (PIs) and the integrase inhibitor Isentress (raltegravir).