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J Acquir Immune Defic Syndr. 2008 Dec 15;49(5):513-9. doi: 10.1097/QAI.0b013e318183a425.

Efavirenz induces CYP2B6-mediated hydroxylation of bupropion in healthy subjects.

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Office of Clinical Pharmacology, US Food and Drug Administration, Silver Spring, MD 20993, USA.



To characterize the effect of efavirenz on bupropion hydroxylation as a marker of cytochrome P450 (CYP) 2B6 activity in healthy subjects.


Thirteen subjects received a single oral dose of bupropion SR 150 mg before and after 2 weeks of efavirenz administration for comparison of bupropion and hydroxybupropion pharmacokinetics. Efavirenz plasma concentrations were also assessed. Subjects were genotyped for CYP2B6 (G516T, C1459T, and A785G), CYP3A4 (A-392G), CYP3A5 (A6986G), and multidrug resistance protein 1 (C3435T).


The area under the concentration vs. time curve ratio of hydroxybupropion:bupropion increased 2.3-fold after efavirenz administration (P=0.0001). Bupropion area under the concentration vs. time curve and Cmax decreased by 55% and 34%, respectively (P<0.002). None of the CYP2B6 or CYP3A genotypes evaluated were associated with a difference in bupropion or efavirenz clearance. The 2 individuals homozygous for multidrug resistance protein 1 3435-T/T had 2.5- and 1.8-fold greater bupropion and efavirenz clearance, respectively, relative to C/C and C/T individuals (P<0.05).


Our results confirm that efavirenz induces CYP2B6 enzyme activity in vivo, as demonstrated by an increase in bupropion hydroxylation after 2 weeks of efavirenz administration.

[Indexed for MEDLINE]

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