Coadministration has not been studied. Clopidogrel is a prodrug and is converted to its active metabolites via CYPs 3A4, 2B6, 2C19 and 1A2. Recurrent drug-eluting in-stent restenosis was described in a HIV patient treated concurrently with etravirine and clopidogrel (possibly due to inhibition of CYP2C19 and thereby decreased conversion of clopidogrel to its active metabolite). Since efavirenz is an inhibitor of CYP2C19, a similar effect cannot be excluded, therefore coadministration is not recommended. Furthermore, clopidogrel is an inhibitor of CYP2B6 and has been shown to increase efavirenz exposure (17% increase in AUC, 31% increase in Cmax).