Phenytoin is a medication primarily used to control seizures in individuals with epilepsy. It works by stabilizing electrical activity in the brain, helping to prevent the rapid firing of neurons that can lead to seizures. Phenytoin is often prescribed for various types of seizures, including tonic-clonic and partial seizures. This medication is usually taken orally in the form of tablets or capsules, but it can also be administered intravenously in a hospital setting. Common side effects may include dizziness, drowsiness, and gum overgrowth. Regular monitoring of blood levels is important to ensure its effectiveness and safety.