Comparative evaluation of anticonvulsant activity of calcium channel blockers in experimental animals.

Pentylenetetrazole (PTZ)-induced convulsions and the maximal electroshock (MES) seizure test were employed to study the anticonvulsant effects of nifedipine (2, 3.5 and 5 mg kg-1), flunarizine (10, 20 and 40 mg kg-1) and diltiazem (10, 15 and 30 mg kg-1). Nifedipine and flunarizine prolonged the latent period and reduced the mean duration of PTZ induced seizures. They also reduced the severity of convulsions and the number of deaths due to PTZ significantly. Nifedipine was more potent in this regard (P < 0.01). All these drugs prolonged the latent period and reduced the duration of tonic extensor phase of MES seizures in a significant manner. Flunarizine was most potent in this test. Complete protection from tonic extensor phase was observed in 10-50% animals pretreated with nifedipine and flunarizine in a dose dependent manner. The response of diltiazem was weak in both these tests. It is concluded that all three calcium channel blockers possess an important but different anticonvulsant effect and their significant clinical use can be made while keeping in view the characteristics of their pharmacological action.