n. any of a group of drugs developed primarily to control epileptic seizures. They were introduced in 1938 after careful studies of chemicals capable of suppressing electroshock convulsions without also causing adverse effects on the central nervous system. Hydantoin molecules are similar in structure to barbiturates but have the advantage of not altering the threshold for minimal seizures. The prototype of the hydantoins is phenytoin (previously called diphenylhydantoin). Other hydantoins include mephenytoin (U.S. trade name: Mesantoin) and ethotoin (U.S. trade name: Peganone), but these are rarely used.