Female gonadal sex steroids potentiate the anti-convulsant activity of phenytoin sodium.

Neither estrogen (E), progesterone (P), E + P nor phenytoin could protect the rats against maximal electroshock seizure. However phenytoin administration in the E, P, or E + P pre-treated animals provided significant protection in terms of absence of hind limb extension and a decrease in the extension/flexion ratio. The results suggest that there is an existing beneficial influence of the oral contraceptives both individually and in combination on the anti-convulsant activity of phenytoin, and this needs to be further probed.