Nimodipine can be used to treat conditions such as aneurysms, subarachnoid hemorrhage, acute myocardial infarction, arrhythmia, hypertension, congestive heart failure, hypertrophic cardiomyopathy, vasospastic angina and Prenzmetal's angina. The purpose of this study was to investigate the effects of cosolvents and surfactants on the pharmacokinetics of nimodipine in rats. A single dose of nimodipine was administered orally (15 mg/kg) to rats in 20 % w/v cosolvent and 1 % w/v surfactant solution respectively. Compared with the control group, the area under the plasma concentration-time curve (AUC0-∞) of nimodipine and the peak plasma concentration (Cmax) were increased significantly (p<0.05) by both vehicles. The relative bioavailability (RB) of nimodipine was 2.4- fold and 3.4- fold greater than that of the control group for propylene glycol and sodium lauryl sulfate respectively. 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. The study suggests that cosolvent (glycerol or propylene glycol) and/or surfactant (polysorbate-80 or sodium lauryl sulfate) could be incorporated into pharmaceutical formulations containing nimodipine.