Phenytoin sodium is a commonly used antiepileptic. Phenytoin (fA``nit'oin, IPA) acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels. Aside from seizures, it is an option in the treatment of trigeminal neuralgia in the event that carbamazepine or other 1st line treatment is deemed inappropriate. Synonyms: Dilantin.