Metabolism of 1'- and 4-hydroxymidazolam by glucuronide conjugation is largely mediated by UDP-glucuronosyltransferases 1A4, 2B4, and 2B7.

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Seo KA, Bae SK, Choi YK, Choi CS, Liu KH, Shin JG

Metabolism of 1'- and 4-hydroxymidazolam by glucuronide conjugation is largely mediated by UDP-glucuronosyltransferases 1A4, 2B4, and 2B7.

Drug Metab Dispos. 2010 Nov;38(11):2007-13. doi: 10.1124/dmd.110.035295. Epub 2010 Aug 16.

PubMed ID

20713656 [ View in PubMed

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Abstract

Midazolam undergoes oxidative hydroxylation by CYP3A to its metabolites, which are excreted mainly as glucuronidated conjugates into the urine. In this study, we examined the glucuronidation of hydroxymidazolam in human liver microsomes (HLMs) and characterized the UDP-glucuronosyltransferases (UGTs) involved in 1'- and 4-hydroxymidazolam glucuronidation. Among the 12 UGT isoforms tested, the O- and N-glucuronidation of 1'-hydroxymidazolam was mediated by UGT2B4/2B7 and 1A4, respectively. In contrast, the glucuronidation of 4-hydroxymidazolam was mediated by UGT1A4. Consistent with these observations, the UGT1A4 inhibitor hecogenin and the UGT2B7 substrate diclofenac potently inhibited the N- and O-glucuronidation of 1'-hydroxymidazolam in HLMs, respectively. A correlation analysis of UGT enzymatic activity and the formation rate of glucuronide metabolites from 1'- and 4-hydroxymidazolam in 25 HLMs showed that hydroxymidazolam glucuronidation is correlated with UGT1A4-mediated lamotrigine glucuronidation and UGT2B7-mediated diclofenac glucuronidation activity. Taken together, these findings indicate that UGT1A4, 2B4, and 2B7 are major isoforms responsible for glucuronide conjugate formation from 1'- and 4-hydroxymidazolam, which are the two major oxidative metabolites of midazolam.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Midazolam	UDP-glucuronosyltransferase 1-4	Protein	Humans	No	Substrate	Details