dizepam metabolism in human foetal and adult liver diazepam was metabolized by human foetal liver microsomes to ndesmethyldiazepam and nmethyloxazepam as early as the 13th week of gestation the metabolic activity was lower than that of microsomes from adult human liver diazepam was shown mainly to be hydroxylated to nmethyloxazepam at substrate concentrations higher than 01 mm diazepam levels above 10 mm were inhibitory to the overall metabolic reaction skf 525a inhibited diazepam metabolism by foetal liver microsomes at a concentration of 01 mm the addition of diazepam to foetal and adult human liver microsomes resulted in a type ii spectral change its inhibition by carbon monoxide indicated that biotransformation of diazepam was performed by the cytochrome p450linked monooxygenase system