Phenytoin is a widely used and effective treatment for epilepsy in people of all ages. It can be used alone or with other seizure medicines to control:

• Partial seizures
• Primary generalized tonic-clonic seizures (grand mal)

Phenytoin is best used for partial-onset seizures—that is, seizures that begin in a limited area of the brain. Sometimes these seizures spread throughout the brain (generalize). Phenytoin generally is not effective against absence seizures and infantile spasms.

Phenytoin may be somewhat helpful in treating clonic, myoclonic, and atonic seizures. It also may help with some types of seizures that occur as part of epilepsy syndromes like the Lennox-Gastaut syndrome.