In vitro metabolism of quazepam in human liver and intestine and assessment of drug interactions.

Article Details

Citation

Miura M, Ohkubo T

In vitro metabolism of quazepam in human liver and intestine and assessment of drug interactions.

Xenobiotica. 2004 Nov-Dec;34(11-12):1001-11.

PubMed ID
15801544 [ View in PubMed
]
Abstract

The study was carried out to identify and characterize kinetically the cytochrome P450 (CYP) enzymes responsible for the major metabolite formation of quazepam. In in vitro studies using human liver and intestinal microsomes and cDNA-expressed human CYP and FMO isoenzymes, quazepam was rapidly metabolized mainly by CYP3A4 and to a minor extent by CYP2C9, CYP2C19 and FMO1 to 2-oxoquazepam (OQ), which was then further biotransformed to N-desalkyl-2-oxoquazepam (DOQ) and to 3-hydroxy-2-oxoquazepam (HOQ) mainly by CYP3A4 and CYP2C9. CYP3A4 is the enzyme predominantly responsible for all the metabolic pathways of quazepam. Itraconazole inhibited the formation of OQ from quazepam, HOQ from OQ and DOQ from OQ in human liver microsomes with Ki values of 8.40, 0.08 and 0.39 microM, respectively. However, the Ki for OQ formation was greater than the peak plasma itraconazole concentration following a clinically relevant 200-mg oral dose to healthy volunteers. In addition, CYP2C9 and CYP2C19 inhibitors failed to inhibit OQ formation from quazepam. In conclusion, clinically relevant drug interaction with CYP inhibitors seem unlikely for the major metabolic pathway of quazepam to OQ.

DrugBank Data that Cites this Article

Drugs
Drug Enzymes
DrugEnzymeKindOrganismPharmacological ActionActions
QuazepamCytochrome P450 2C19ProteinHumans
No
Substrate
Details
QuazepamCytochrome P450 3A4ProteinHumans
No
Substrate
Details
Drug Reactions
Reaction
Details