Efavirenz/emtricitabine/tenofovir disoproxil (Atripla)

Atripla is a fixed-dose tablet combining 600mg efavirenz, 200mg FTC (emtricitabine), and 245mg tenofovir, manufactured jointly by Bristol-Myers Squibb and Gilead Sciences. Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI), FTC is a nucleoside reverse transcriptase inhibitor (NRTI), and tenofovir is a nucleotide reverse transcriptase inhibitor (NtRTI). These drugs reduce the amount of HIV in the body and prevent the development of AIDS-defining illnesses .

The standard dose of Atripla is one tablet once a day. The manufacturers advise patients to take the tablet on an empty stomach before going to bed.

Atripla is the first combination tablet to be licensed for use in Europe and the United States that provides all the drugs needed for an anti-HIV regimen, achieving the goal of one tablet once a day to treat HIV infection. It was licensed in the United States for use in HIV-positive adults in 2006 and approved for use in the European Union in late 2007.

In the European Union Atripla is licensed for use in patients who have already achieved undetectable viral load on a combination in which Atripla's components are dosed separately as Truvada and efavirenz. In the United States Atripla can be used as initial therapy without the need for an induction phase using separate components. The European medicines licensing body has not issued an explanation of its divergent licensing decision.

Atripla was licensed on the basis of data from Study 934, that compared efavirenz (Sustiva), FTC (Emtriva) and tenofovir (Viread) taken as separate drugs, to the combination of efavirenz and AZT (zidovudine) plus 3TC (lamivudine) as Combivir. In this study, more patients in the FTC and tenofovir arm achieved viral loads below 400 copies/ml after 48 weeks, largely due to fewer discontinuations due to drug side-effects. A study in HIV-negative subjects revealed that the triple combination tablet produces blood levels equivalent to the three drugs taken separately.

The main side-effects of Atripla are dizziness, nausea, diarrhoea, fatigue, headache, and rash. It should not be used by women during the first three months of pregnancy, due to a risk of birth abnormalities caused by efavirenz. It should not be taken by patients with kidney problems (creatine clearance less than 50ml/min).

Atripla should not be used in adults with creatinine clearance of <50ml/minute or in paediatric patients weighing less than 40 kilograms.

Because of the efavirenz component in Atripla, use of many drugs is counterindicated or may require dosing adjustment. Please review the drug interaction section for efavirenz in A to Z of antiretroviral drugs.

For more information on Atripla's component drugs, including drug interactions, side-effects and resistance, see efavirenz (Sustiva), FTC (emtricitabine, Emtriva) and tenofovir (Viread).