Hydantoin derivatives are commonly used anticonvulsant drugs. It is generally effective against partial and tonic-clonic seizures but not in absent seizures. Phenytoin is the main drug of this group and other drugs ethotoin, mephenytoin also commonly used in the therapy of epilepsies. However, they have some adverse effects and long period of therapy to seizure control. To sort out these problems, various new hydantoin derivatives as well as prodrugs like fosphenytoin were prepared. Phenytoin is effective in some cases of trigeminal and related neuralgias. Phenytoin is also used in the treatment of cardiac arrhythmias.