PT - JOURNAL ARTICLE AU - G M Pacifici AU - A Rane TI - Inhibition of morphine glucuronidation by oxazepam in human fetal liver microsomes. DP - 1981 Nov 01 TA - Drug Metabolism and Disposition PG - 569--572 VI - 9 IP - 6 4099 - http://dmd.aspetjournals.org/content/9/6/569.short 4100 - http://dmd.aspetjournals.org/content/9/6/569.full SO - Drug Metab Dispos1981 Nov 01; 9 AB - Uridine diphosphoglucuronyltransferase activity toward morphine was measured in vitro in preparations of human fetal liver microsomes. The inhibition of the glucuronidation of morphine was studied at concentrations of morphine and uridine diphosphoglucuronic acid of 3 and 15 mM, respectively. Oxazepam inhibited the reaction by about 50% at concentration of 0.3 mM. The inhibition was almost complete when the concentration was 3 mM, i.e., the same as for morphine. Salicylamide was considerably less potent as an inhibitor of morphine glucuronidation with an almost 100-fold difference in potency as compared to oxazepam. Lineweaver-Burk plots of the inhibition data revealed that oxazepam exerts a competitive type of inhibition with an apparent Ki value of 0.2 mM.