Effect of nimodipine on the efficacy of commonly used antiepileptic drugs in rats.

Effect of nimodipine was studied alone and in combination with phenytoin and valproate in maximal electroshock seizures in rats. The test drug was injected i.p. and seizures elicited by a 60 Hz alternating current of 150 mA intensity for 0.25 sec duration through corneal electrodes. The median effective dose (ED50) of phenytoin, valproate and nimodipine were found to be 13, 255 and 4 mg/kg respectively. Addition of ED50 of nimodipine to ED50 of phenytoin and valproate produced an additive effect. Addition of ED25 of nimodipine to ED25 of phenytoin and valproate produced asynergistic effect. Our results show that addition of nimodipine significantly potentiates the anticonvulsant efficacy of phenytoin and valproate.