Abstract 5-Ethyl-5-(p-hydroxyphenyl) hydantoin (" p-hydroxynirvanol") has been found in the urine of dogs after the administration of 3-methyl-5-ethyl-5-phenyl hydantoin (Mesantoin) or 5-ethyl-5-phenyl hydantoin (Nirvanol). The same product has been isolated from the urine of a man receiving Mesantoin.
