Effect of nimodipine, a dihydropyridine calcium channel antahgonists, on the steady state pharmacokinetrics of phenytoin (DPH) in rhesus monkeys

Nimodipine, a dihydropyridine calcium channel blocker, has been shown to cause a potentiation of anticonvulsant action of phenytoin (DPH) against maximal electroshock-induced seizures in rats. This crossover study was carried out in rhesus monkeys to determine if any pharmacokinetic interaction was involved in such a potentiation. The steady state pharmacokinetics of phenytoin was examined before and after nimodipine administration. No significant differences were observed in plasma concentration of phenytoin at different time points nor in any of the pharmacokinetic parameters in the two groups. The results reveal that the potentiation of anticonvulsant action of phenytoin by nimodipine is probably due to a pharmacodynamic interaction between the two drugs.