PHARMACOKINETIC STEREOSELECTIVITY OF TROGLITAZONE, AN ANTIDIABETIC AGENT, IN THE KK MOUSE

✍ Scribed by T. IZUMI; S. ENOMOTO; K. HOSHIYAMA; K. SASAHARA; Y. SUGIYAMA

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 266 KB
• Volume: 18
• Category: Article
• ISSN: 0142-2782
• DOI: 10.1002/(sici)1099-081x(199705)18:4<305::aid-bdd19>3.0.co;2-l

✦ Synopsis

Troglitazone, an oral antidiabetic agent, is an equal mixture of four stereoisomers involving two asymmetric centres. In the present study, the stereoselectivity of in vitro epimerization in plasma and organ homogenate and in vivo plasma disposition in the KK mouse, an animal model of non-insulin-dependent diabetes, was examined. In the incubation experiments at 37 8C, there was a ®vefold to eightfold acceleration of epimerization at the 5 position of the thiazolidine ring in KK mouse plasma compared with that in buer. However, no inversion at the 2 position of the chroman ring was observed. In addition, there was an approximately 1´3-fold dierence in the epimerization rates among stereoisomers at the 2 position of the chroman ring. However, there were no dierences in the values of the equilibrium constants of epimerization, and the ratio of epimerization among stereoisomers at the 5 position of thiazolidine ring was almost unity. The acceleration of epimerization is thought to be due to the high degree of protein binding because of the relationship between the initial epimerization rate and the dilution ratio of the plasma. Although acceleration of epimerization was also observed in the 20% homogenates of liver, kidney, and intestine of the KK mouse, the degree of stereoselectivity was lower than in plasma.

The analysis of the plasma disposition after intravenous administration of troglitazone stereoisomers, using a kinetic model, indicated that the metabolic clearance in the liver showed a 2´5-fold maximum dierence among stereoisomers and that the stereoselectivity of epimerization was low. &1997 by John Wiley & Sons, Ltd.