Phenytoin (PHT), sold under the brand name Dilantin among others, [1] is an anti-seizure medication. [3] It is useful for the prevention of tonic-clonic seizures (also known as grand mal seizures) and focal seizures, but not absence seizures. [3] Phenytoin is one of the oldest and most widely used antiepileptic drugs (AEDs), primarily for treating focal seizures and generalized tonic-clonic seizures. It has a well-known profile, acting on voltage-gated sodium channels to reduce high-frequency neuronal firing. Phenytoin is used to control certain type of seizures, and to treat and prevent seizures that may begin during or after surgery to the brain or nervous system. Phenytoin is in a class of medications called anticonvulsants. Phenytoin is an anti-epileptic drug, also called an anticonvulsant. Phenytoin works by slowing down impulses in the brain that cause seizures. Phenytoin is used to control seizures. It does not treat all types of seizures, and your doctor will determine if it is the right medicine for you. Phenytoin is used to control seizures (convulsions), including tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures, in the treatment of epilepsy. It is also used to prevent and treat seizures that occur during brain surgery. Phenytoin is used to treat certain types of seizures. Common side effects include drowsiness, confusion, slurred speech, trouble with balance or coordination, and uncontrollable eye movements. Phenytoin is used to prevent and control seizures (also called an anticonvulsant or antiepileptic drug). It works by reducing the spread of seizure activity in the brain. Learn about side effects, dosages, drug interactions, and more.