Pharmacokinetics of chlorzoxazone in rats with diabetes: Induction of CYP2E1 on 6-hydroxychlorzoxazone formation

Pharmacokinetic parameters of chlorzoxazone (CZX) and its main metabolite, 6-hydroxychlorzoxazone (OH-CZX), were compared after intravenous (20 mg/kg) and oral (50 mg/kg) administration of CZX in rat model of diabetes induced by alloxan (DMIA) or streptozotocin (DMIS), and their respective control rats. In both rat models of diabetes, the expression and mRNA level of CYP2E1 increased, and CZX was metabolized to OH-CZX via CYP2E1 in rats. Hence, it could be expected that formation of OH-CZX increased in both rat models of diabetes. As expected, after intravenous (80.5% and 74.4% increase in rat models of DMIA and DMIS, respectively) and oral (55.6% and 70.5% increase, respectively) administration of CZX, the AUC of OH-CZX was significantly greater than their respective control rats. Since, CZX is an intermediate hepatic extraction ratio drug, the greater AUC values of OH-CZX (the significantly faster CLNR of CZX) in both rat models of diabetes could be supported by significantly faster CLint for the formation of OH-CZX (75.9% and 129% increase for rat models of DMIA and DMIS, respectively) and significantly greater free fractions of CZX in plasma (51.9% and 58.9% increase, respectively). Also it was reported that hepatic blood flow rate was faster in male Wister rat model of DMIS. (c) 2006 Wiley-Liss, Inc. and the American Pharmacists Association.