In vivo comparison of estradiol metabolism in liver microsomes of human, Beagle dog and rat / 药学学报

The inter-species differences of estradiol metabolism were investigated in human, Beagle dog and rat liver microsomes by comparing enzyme kinetics of parent drug and the formation of its major metabolites. The incubation systems of estradiol with liver microsomes of the three species were optimized in terms of estradiol concentration, microsomal protein content and incubation time. The concentrations of estradiol and its metabolites were measured by LC-MS/MS method. The t1/2, CLint, CLh, Km and Vmax of estradiol incubated with male human liver microsomes were 40.02 +/- 8.32 min, 41.39 +/- 6.57 mL x min(-1) x kg(-1), 13.81 +/- 12.36 mL x min(-1) x kg(-1), 26.8 +/- 6.99 micromol x L(-1) and 0.75 +/- 0.92 micromol x L(-1) x min(-1), respectively. The corresponding parameters of female human were 44.71 +/- 10.21 min, 29.85 +/- 8.97 mL x min(-1) x kg(-1), 0.01 +/- 0.68 mL x min(-1) x kg(-1), 44.2 +/- 7.73 micromol x L(-1) and 1.27 +/- 4.41 micromol x L(-1) x min(-1), that of male dog were 21 +/- 7.33 min, 165.53 +/- 29.33 mL x min(-1) xkg(-1), 26.01 +/- 8.39 mL x min(-1) x kg(-1), 19.5 +/- 7.34 micromol x L(-1) and 1.6 +/- 0.65 micromol x L(-1) x min(-1), that of female dog were 25.5 +/- 5.32 min, 135.11 +/- 42.34 mL x min(-1) x kg(-1), 0.24 +/- 3.18 mL x min(-1) x kg(-1), 8.33 +/- 6.32 micromol x L(-1) and 0.51 +/- 2.15 micromol x L(-1) x min(-1), that of male rat were 5.11 +/- 3.84 min, 485.63 +/- 36.52 mL x min(-1) x kg(-1), 49.57 +/- 15.29 mL x min(-1) x kg(-1), 62 +/- 13.74 micromol x L(-1) and 19.16 +/- 9.67 micromol x L(-1) x min(-1), and that of female rat were 7.0 +/- 3.69 min, 354.82 +/- 33.33 mL x min(-1) x kg(-1), 8.04 +/- 3.23 mL x min(-1) x kg(-1), 35.38 +/- 7.65 micromol x L(-1) and 8.39 +/- 4.91 micromol x L(-1) min(-1), respectively. There were nine metabolites detected from all the three species, but the relative amounts of the metabolites generated were different in three species. The results indicted that the major phase I metabolic pathway of estradiol was similar in the liver microsomes from all the three species. However, the inter-species differences were found in the view of relative amounts of the metabolites as well as the metabolic characteristics of estradiol in liver microsomal incubation.

CYP450 induction based drug-drug interaction and evaluation methodology / 国际药学研究杂志

Drug discovery and development is an expensive process with a high attrition rate. Cytochrome P450 (CYP) induction and inhibition mediated drug-drug interaction of drug candidates serves as one of the reasons for such attrition. Consequently a great effort is paid to identify those compounds that influence pharmacokinetic parameters of other drugs, which may lead to drug-drug interactions. CYP plays a central role in metabolism and biosynthesis of a wide range of exogenous and endogenous compounds. CYP induction mediated drug-drug interactions may result in an increased metabolic clearance for coadministrated drugs, and subsequently affect their effectiveness and safety. Assessment of CYP induction potential for drug candidates has become an integral part of new drug discovery and development. This article reviews the current understanding on CYP induction mediated drug-drug interaction and its clinical implications, along with the in vitro and in vivo methodologies for assessment of the induction potential of new drug candidates.