Inhibition of human drug metabolizing cytochrome P450 by buprenorphine

The effects of buprenorphine, a powerful mixed agonist/antagonist analgesic, on several cytochrome P450 (CYP) isoform specific reactions in human liver microsomes were investigated to predict drug Interaction of buprenorphine in vivo from in vitro data. The following eight CYP-catalytic reactions were used in this study: CYP1A1/2-mediated 7-ethoxyresorufin O-deethylation, CYP2A6-mediated coumarin 7-hydroxylation, CYP2B6-mediated 7-benzyloxyresorufin O-debenzylation, CYP2C8/9-mediated tolbutamide methy1hydroxylation, CYP2C19-mediated S-mephenytoin 4-hydroxylation, CYP2D6-mediated bufuralol 1'-hydroxylation, CYP2E1-mediated chlorzoxazone 6-hydroxylation, and CYP3A4-mediated testosterone 6beta-hydroxylation. Buprenorphine strongly inhibited the CYP3A4- and CYP2D6-catalyzed reactions with Ki values of 14.7 muM and 21.4 muM, respectively. The analgesic also weakly inhibited specific reactions catalyzed by CYP1A1/2 (Ki=132 muM), CYP2B6 (Ki=133 muM), CYP2C19 (Ki=146 muM), CYP2C8/9 (IC50>300 muM), and CYP2E1 (IC50>300 muM), but not CYP2A6 mediated pathway. In consideration of the Ki values obtained in this study and the therapeutic concentration of buprenorphine in human plasma, buprenorphine would not be predicted to cause clinically significant interactions with other CYP-metabolized drugs.