This is an anticonvulsant or antiepileptic drug. It acts by reducing the sensitivity of neurological cells, thereby preventing the electrical impulses that flash through the brain causing epilepsy. It is an extremely effective and successful drug, although some side effects are associated.
Phenytoin is usually only prescribed by specialists when no other options are available. Treatment, once started, should be continued until your specialist or GP removes you from the drug. It is worthwhile discussing the underlying problem with a complementary medical practitioner but stopping any anticonvulsant is a risky business.