Abstract
Buprenorphine (BN) is a thebaine derivative with analgesic properties. To identify and characterize the cytochrome P450 (CYP) enzyme(s) involved in BN N-dealkylation, in vitro studies using human liver microsomes and recombinant human CYP enzymes were performed. Norbuprenorphine formation from BN was measured by a simple HPLC-UV assay method, without extraction. The BNN-dealkylation activities in 10 human liver microsomal preparations were strongly correlated with microsomal CYP3A-specific metabolic reactions, i.e. triazolam 1′-hydroxylation (r = 0.954), midazolam 1′-hydroxylation (r = 0.928), and testosterone 6β-hydroxylation (r = 0.897). Among the eight recombinant CYP enzymes studied (CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4), only CYP3A4 could catalyze BN N-dealkylation. The apparent KM value for recombinant CYP3A4 was similar to that for human liver microsomes (23.7 vs.39.3 ± 9.2 μM). The demonstration of BNN-dealkylation by recombinant CYP3A4 and the agreement in the affinities (apparent KM values) of human liver microsomes and recombinant CYP3A4 provide the most supportive evidence for BN N-dealkylation being catalyzed by CYP3A4.
Footnotes
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Send reprint requests to: Prof. Toshinori Yamamoto, Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Showa University, Hatanodai 1–5-8, Shinagawa-ku, Tokyo 142, Japan.
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This study was supported by a Grant-in-aid for Encouragement of Young Scientists from the Ministry of Education and Science (Grant 06772215), by the Japan Health Science Foundation (Grant 1–7-1-C), and by the Drug Innovation Science Project (Grant 1–2-10) (Tokyo, Japan).
- Abbreviations used are::
- BN
- buprenorphine
- NBN
- norbuprenorphine
- CYP
- cytochrome P450
- Received August 15, 1997.
- Accepted March 14, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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