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Published on: September 1, 2016
Lack of interaction of buprenorphine with flunitrazepam metabolism
1Department of Pharmacology, University of Toronto, Ontario, Canada.
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.
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