Effects of pravastatin on the pharmacokinetic parameters of nimodipine after oral and intravenous administration in rats: Possible role of CYP3A4 inhibition by pravastatin

OBJECTIVE: The aim of this study was to investigate the effects of pravastatin on the pharmacokinetics of nimodipine in rats. MATERIALS AND METHODS: The effect of pravastatin on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity was evaluated. Nimodipine was administered to rats intravenously (3 mg/kg) and orally (12 mg/kg) with pravastatin (0.3 and 1 mg/kg). RESULTS: Pravastatin inhibited CYP3A4 enzyme activity in a concentration-dependent manner with a 50% inhibition concentration (IC(50)) of 14 µM. Compared with the oral control group, the area under the plasma concentration-time curve (AUC(0-∞)) of nimodipine was increased significantly. Consequently, the absolute bioavailability (AB) of nimodipine with pravastatin (1 mg/kg) was 31.1%, which was significantly enhanced compared with the oral control group. Moreover, the relative bioavailability (RB) of nimodipine was 1.12- to 1.31-fold greater than that of the control group. CONCLUSIONS: The enhanced oral bioavailability of nimodipine might be mainly due to inhibition of the CYP3A-mediated metabolism of nimodipine in the small intestine and/or in the liver and due to reduction of the total body clearance rather than both to inhibition of the P-gp efflux transporter in the small intestine and reduction of renal elimination of nimodipine by pravastatin. The increase in the oral bioavailability of nimodipine with pravastatin should be taken into consideration of potential drug interactions between nimodipine and pravastatin.