Gemfibrozil and its oxidative metabolites: quantification of aglycones, acyl glucuronides, and covalent adducts in samples from preclinical and clinical kinetic studies

A gradient reversed-phase HPLC analysis for the direct measurement of gemfi brozil (GEM) and four oxidative metabolites in plasma and urine of humans a nd in tissue homogenates of rats was developed. The corresponding acyl gluc uronides and the covalently bound protein adducts (in protein precipitates) were determined after liberation from the respective conjugates via alkali ne hydrolysis. The limits of detection for the covalent adducts in human pl asma are: 10 ng ml(-1) (GEM), 20 ng ml(-1) (M1), 0.5 ng ml(-1) (M2, M4), an d 5 ng ml(-1) (M3). The method was validated with respect to selectivity, r ecovery, linearity, precision, and accuracy. It has been applied to the ana lysis of preclinical and clinical studies. Pharmacokinetic profiles of gemf ibrozil, its metabolites, and covalent adducts in human plasma and rat tiss ue homogenates are given. (C) 2000 Elsevier Science B.V. All rights reserve d.