The objective of this study was to elucidate the chemical structure of the metabolites derived from lobeglitazone (LB) during its incubation with rat liver microsomes and to characterize the kinetics of formation of the major metabolite M1 in vivo. Using high performance liquid chromatography coupled with a hybrid quadrupole linear ion trap, the metabolites were derived from LB during its incubation with rat liver microsomes. From various fragmentation patterns obtained from the metabolites, LB was biotransformed into 5 metabolites in the incubation, in which demethylation and hydroxylation appeared to be the principle metabolic pathways in vitro; Amongst the five primary metabolites, M1, a demethylated derivative of LB, appeared to be the major metabolite of LB, based on a comparison on the peak intensities in the ion chromatogram. In a study of the in vivo kinetics of formation of M1 in rats, the rate of formation of M1 from LB was determined to be 0.252 and 0.216mL/min/kg at doses of 0.5mg/kg and 2mg/kg of LB, respectively, suggesting that the kinetics of M1 formation were linear in the dose range tested. Considering the fact that LB is primarily eliminated by hepatic metabolism in rats, the formation of M1 accounts for approximately 7.50-9.76% of the overall elimination of LB in rats.
Keywords: Formation clearance; Lobeglitazone; Metabolite identification; Pharmacokinetics; Rat liver microsome.
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