T Kilicarslan1, E M Sellers. 1. Department of Pharmacology, University of Toronto, Ontario, Canada.
Abstract
OBJECTIVE: The authors' goal was to determine if the reported clinical adverse interaction of flunitrazepam and buprenorphine was caused by inhibition of drug metabolism. METHOD: Inhibition of flunitrazepam metabolism by buprenorphine and norbuprenorphine were determined in three human liver microsome preparations carrying the CYP2C19*1/*1 allele. Omeprazole metabolism mediated by CYP2C19 and CYP3A4 was used as a control reaction. Apparent K(i) values were determined. RESULTS: Norbuprenorphine did not inhibit the metabolism of flunitrazepam or omeprazole. Buprenorphine inhibited the formation of CYP3A4-mediated pathways of 3-hydroxyflunitrazepam and omeprazole sulfone formation (K(i) 118 and 16 microM) in human liver microsomes. Corresponding values were 38 and 90 microM in cDNA-expressed CYP3A4 microsomes. Projected in vivo inhibition of CYP3A4-mediated metabolism of flunitrazepam by buprenorphine is 0. 1%-2.5%. Estimated inhibition of buprenorphine N-dealkylation by flunitrazepam in vivo is 0.08%. CONCLUSIONS: The clinical interaction of flunitrazepam and buprenorphine is likely based on a pharmacodynamic mechanism.
OBJECTIVE: The authors' goal was to determine if the reported clinical adverse interaction of flunitrazepam and buprenorphine was caused by inhibition of drug metabolism. METHOD: Inhibition of flunitrazepam metabolism by buprenorphine and norbuprenorphine were determined in three human liver microsome preparations carrying the CYP2C19*1/*1 allele. Omeprazole metabolism mediated by CYP2C19 and CYP3A4 was used as a control reaction. Apparent K(i) values were determined. RESULTS:Norbuprenorphine did not inhibit the metabolism of flunitrazepam or omeprazole. Buprenorphine inhibited the formation of CYP3A4-mediated pathways of 3-hydroxyflunitrazepam and omeprazole sulfone formation (K(i) 118 and 16 microM) in human liver microsomes. Corresponding values were 38 and 90 microM in cDNA-expressed CYP3A4 microsomes. Projected in vivo inhibition of CYP3A4-mediated metabolism of flunitrazepam by buprenorphine is 0. 1%-2.5%. Estimated inhibition of buprenorphine N-dealkylation by flunitrazepam in vivo is 0.08%. CONCLUSIONS: The clinical interaction of flunitrazepam and buprenorphine is likely based on a pharmacodynamic mechanism.
Authors: Hendree E Jones; Peter R Martin; Sarah H Heil; Karol Kaltenbach; Peter Selby; Mara G Coyle; Susan M Stine; Kevin E O'Grady; Amelia M Arria; Gabriele Fischer Journal: J Subst Abuse Treat Date: 2008-01-14