in vitro metabolism of quazepam in human liver and intestine and assessment of drug interactions 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 cdnaexpressed human cyp and fmo isoenzymes quazepam was rapidly metabolized mainly by cyp3a4 and to a minor extent by cyp2c9 cyp2c19 and fmo1 to 2oxoquazepam oq which was then further biotransformed to ndesalkyl2oxoquazepam doq and to 3hydroxy2oxoquazepam 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 840 008 and 039 microm respectively however the ki for oq formation was greater than the peak plasma itraconazole concentration following a clinically relevant 200mg 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