hydantoin /hīdan″tō·in/ , any one of a group of anticonvulsant medications, chemically and pharmacologically similar to the barbiturates, that acts to limit seizure activity and reduce the spreading of abnormal electrical excitation from the focus of the seizure. A primary hydantoin in the management of almost all forms of epilepsy is phenytoin, formerly known as diphenylhydantoin. Frequent determination of the blood concentration of hydantoin is necessary.
