Phenytoin is a hydantoin anticonvulsant drug, long used as the sodium salt in the therapy for epilepsy in the management of generalized tonic-clonic and complex partial seizures. It also has utility in the prevention of seizures following head trauma. The drug is available by prescription under the trade names Dilantin®, Phenytek®, and Epanutin®, among others. Phenytoin has been studied extensively in the laboratory with six species of animals assessed. In the human, a very large number of reports were published associating the administration of phenytoin to epileptic women during pregnancy to developmental toxicity of most all classes, with the exception of viability. In 1964, D. Janz and U. Fuchs reported the first (five) cases of congenital malformation related to phenytoin administration during pregnancy. The mechanism of phenytoin teratogenicity has been the subject of numerous experimental studies. Phenytoin is an average-sized hydrophobic compound. It is of average polarity in comparison to the other human developmental toxicants.