Drug-drug interaction study to assess the effects of atorvastatin co-administration on pharmacokinetics and anti-thrombotic properties of cilostazol in male Wistar rats

Cilostazol (CLZ) and atorvastatin (ATV) are often co-prescribed to treat conditions such as peripheral arterial disease. In the present study, the drugdrug interaction potential of multi-dose ATV co-administration with CLZ on both pharmacokinetics and the anti-thrombotic property of CLZ is demonstrated. The pharmacokinetic parameters of CLZ (6?mg/kg, twice daily) were determined in male Wistar rats after 7?days co-administration with ATV (5?mg/kg, once daily) in order to assess the interaction potential between CLZ and ATV on chronic treatment. In vitro metabolic inhibition and everted gut sac studies were conducted to elucidate the mechanism of this interaction. Pharmacodynamic drugdrug interaction was evaluated on anti-thrombotic models including time to occlusion, platelet aggregation and rat tail bleeding time. A validated LC-MS/MS method was employed simultaneously to quantify both ATV and CLZ in rat plasma matrix. A statistically significant increase in systemic exposure (Cssmax by similar to 1.75 fold; AUC by similar to 3.0 fold) to CLZ was observed in ATV pre-treated rats. In vitro metabolism studies using liver microsomes (RLM and HLM) demonstrated statistically significant inhibition of CLZ metabolism when co-incubated with ATV. No change in apparent permeability of CLZ was observed in the presence of ATV. Atorvastatin showed a significant delay in artery occlusion time without altering CLZ's bleeding time and platelet aggregation profile. Collectively the results of these studies provide metabolic insight into the nature of drugdrug interaction between the selected drugs. Co-administration with ATV influences the pharmacokinetics and anti-thrombotic property of CLZ. A thorough clinical investigation is required before extrapolation of data to humans. Copyright (c) 2012 John Wiley & Sons, Ltd.