Background and Aim: Epilepsy is one of the neurologic abnormalities that involve local or larger structures of the brain. This disease occurs because of electrical hyperactivity of some brain centers or attenuation of inhibitory processes of brain. Despite of extensive neuropharmacologic investigations, desirable treatments in most patients does not occur. Therefore, research on novel anticonvulsant medicine specially plant origin substances is one of the serious goals of related laboratories. Methods: The hydroalcoholic extract of stem and leaves of Ferula szowitziana were prepared. A combination of tween 80, saline and ethanol was used as solvent. 35 male Wistar rat (200-250 g) in five groups including control, sham and three experimental (50, 100 and 200 mg/kg of extract) were used for I.P injections. Seizure was induced by pentylenetetrazol (45 mg/kg/I.P) injection. Finally the latent periods different stages convulsions were recorded according to Racine. Results: Doses of 100 and 200 mg/kg significantly increased the latent period for 3rd stage onset (p<0.05, p<0.001 respectively) and for 4th stage onset (p<0.001, p<0.001 respectively) of seizure. Conclusion: The essential oil of Ferula szowitziana increase the latency period of seizure onset that probably is due to monoterpenes such as α pinene, β pinene, limonene and etc. It has been shown that monoterpenes influences on opioid system and adenosine receptors which creates sedative effect in nervous system, therefore anticonvulsant potential of monoterpenes is expected.

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