Efavirenz (Sustiva) is dosed at 600mg, taken in the form of three 200mg capsules or one 600mg tablet once a day. It can be taken with or without food, but taking the drug with food may increase drug levels in some people by up to 50%. High fat meals may increase the absorption of efavirenz, which may in turn increase the risk of side-effects, especially during the early weeks of treatment.

It is important to take the drug as prescribed in order to maintain the right level of the drug in the blood. If blood levels of the drug fall too low, this will help the development of resistance to efavirenz and may affect future treatment options.

Efavirenz is also available as a solution for use in children and people who cannot take the tablets or capsules.