Enhanced Nimodipine Bioavailability After Oral Administration of Nimodipine with Morin, a Flavonoid, in Rabbits

The aim of this study was to investigate the effect of morin on the bioavailability of nimodipine after administering nimodipine (15 mg/kg) orally to rabbits either co-administered or pretreated with morin (2, 10 and 20 mg/kg). The plasma concentrations of nimodipine in the rabbits pretreated with morin were increased significantly (p<0.05 at 10 mg/kg, p<0.01 at 20 mg/kg) compared with the control, but the plasma concentrations of nimodipine co-administered with morin were not significant. The areas under the plasma concentration-time curve (AUC) and the peak concentrations $(C_{max})$ of the nimodipine in the rabbits pretreated with morin were significantly higher (p<0.05 at 10 mg/kg, p<0.01 at 20 mg/kg), but only the $C_{max}$ of nimodipine coadministered with morin 10 mg/kg was increased significantly (p<0.05). The absolute bioavailability $(A.B\%)$ of nimodipine in the rabbits pretreated with morin was significantly (p<0.05 at 10 mg/kg, p<0.01 at 20 mg/kg) higher $(54.1-65.0\%)$ than the control $(36.7\%)$. The increased bioavailability of nimodipine in the rabbits pretreated with morin might have been resulted from the morin, which inhibits the efflux pump P-glycoprotein and the first-pass metabolizing enzyme by cytochrome P-450 3A4 (CYP 3A4).