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Contribution of the N‐glucuronidation pathway to the overall in vitro metabolic clearance of midazolam in humans
Author(s) -
Klieber Sylvie,
Hugla Sebastien,
Ngo Robert,
ArabeyreFabre Catherine,
Meunier Viviane,
Sadoun Freddy,
Fedeli Olivier,
Rival Martine,
Bourrie Martine,
Guillou Francois,
Maurel Patrick,
Fabre Gerard
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.372.1
Subject(s) - glucuronidation , midazolam , cyp3a4 , chemistry , in vivo , pharmacology , microsome , metabolite , in vitro , glucuronide , cytochrome p450 , metabolic pathway , glucuronosyltransferase , biochemistry , metabolism , biology , microbiology and biotechnology , sedation
Midazolam is one of the most commonly used in vivo and in vitro CYP3A4 probe substrate for drug‐drug interactions studies in humans based on the CYP3A4‐mediation of its 1′‐hydroxylation, a major metabolic pathway. In the present work, the in vitro metabolic pathways of midazolam in humans were studied in details in order to elucidate whether or not an alternative metabolic route such as direct N‐ glucuronidation could be responsible for a metabolic shift between CYP3A4/5 and UGT. Indeed, following incubation of midazolam with human liver microsomes supplemented with UDPGA, two metabolites were identified as quaternary direct β‐ N‐ glucuronides of midazolam. Molecular modelling experiments showed that both glucuronide derivatives were in an atropoisomerism equilibrium. Only isoform UGT1A4 can catalyze this direct N‐ glucuronidation which follows Michaelis‐Menten kinetics. Midazolam‐ N‐ glucuronide was formed in human hepatocytes incubated with and without ketoconazole. Direct midazolam‐ N‐ glucuronidation may partly compensate for the decrease in midazolam metabolic clearance caused by ketoconazole thus potentially leading to a certain extent of misinterpretation of CYP3A4‐mediated DDI study results both in vitro and in vivo .