title: Inhibition of CYP2D6 activity by bupropion.
abstract: The purpose of this study was to assess the effect of bupropion on cytochrome P450 2D6 (CYP2D6) activity. Twenty-one subjects completed this repeated-measures study in which dextromethorphan (30-mg oral dose) was administered to smokers at baseline and after 17 days of treatment with either bupropion sustained-release (150 mg twice daily) or matching placebo. Subjects quit smoking 3 days before the second dextromethorphan administration. To assess CYP2D6 activity, urinary dextromethorphan/dextrorphan metabolic ratios were calculated after an 8-hour urine collection. Thirteen subjects received bupropion, and 8 received placebo. In those receiving active medication, the dextromethorphan/dextrorphan ratio increased significantly at the second assessment relative to the first (0.012 +/- 0.012 vs. 0.418 +/- 0.302; P < 0.0004). No such change was observed in those randomized to placebo (0.009 +/- 0.010 vs. 0.017 +/- 0.015; P = NS). At baseline, all subjects were phenotypically extensive CYP2D6 metabolizers (metabolic ratio <0.3); after treatment, 6 of 13 subjects receiving bupropion, but none of those receiving placebo, had metabolic ratios consistent with poor CYP2D6 metabolizers. Bupropion is therefore a potent inhibitor of CYP2D6 activity, and care should be exercised when initiating or discontinuing bupropion use in patients taking drugs metabolized by CYP2D6.
authors.affiliation: Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Twin Cities Campus, Minneapolis, MN 55455, USA. kotly001@umn.edu
authors.forename: Michael
authors.initials: M
authors.lastname: Kotlyar
authors.forename: Lisa H
authors.initials: LH
authors.lastname: Brauer
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Tracy
authors.forename: Dorothy K
authors.initials: DK
authors.lastname: Hatsukami
authors.forename: Jennifer
authors.initials: J
authors.lastname: Harris
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Bronars
authors.forename: David E
authors.initials: DE
authors.lastname: Adson
mesh_terms: D000328:Adult; D016642:Bupropion / Q000494:pharmacology*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D003915:Dextromethorphan / Q000494:pharmacology / Q000652:urine; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004791:Enzyme Inhibitors; D016642:Bupropion; D003915:Dextromethorphan; D019389:Cytochrome P-450 CYP2D6