ABSTRACT
Mephenytoin (MHT) was marketed in the early 1940s with the belief that it was an effective antiepileptic agent with a somewhat broader profile than phenytoin (PHT) and generally fewer dose-related adverse effects. MHT is an N-methyl substituted hydantoin with phenyl and ethyl groups on the 5 carbon of the hydantoin ring. MHT exhibits protection against both maximal electroshock seizures and pentylenetetrazole-, picrotoxin-, or bicuculline-induced seizures, indicating a broader range of antiepileptic action than PHT. MHT is useful for the same types of seizures as is PHT, namely, all seizures of focal origin and all convulsive seizures, whether they show clinical or electrographic evidence of focality. S-Mephenytoin parahydroxylation is handled by the same saturable mechanism at the same sites as is PHT. The major clinical question concerning the use of MHT revolves around its potential for dangerous adverse effects. The idiosyncratic adverse effects are of greater seriousness and have led to most of the anxiety about MHT.
