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 a medicine used to treat epilepsy. It can also be used to treat trigeminal neuralgia, a type of nerve pain that affects your face. Phenytoin is available on prescription.