5- Ethyl-5-phenylhydantoin

V-Subslilulion and 5,5-disubstitution prevent ring opening as demonstrated by various examples. Ethotoin (3-ethyl-5-phenylhydantoin, 4.230), in contrast to its /V-dcclhylalcd metabolite, was not detectably hydrolyzed by DHPase. No ring-opened metabolite was found for phenytoin (5,5-diphenyl-hydantoin, 4.231) or nirvanol (5-ethyl-5-phenylhydantoin, 4.232), which is the AT-demethylated metabolite of mephenytoin (4.233) [144],... 

Gas Chromatography. System GA—RI 1791 system GE— retention time 0.55 for methoin and 0.73 for 5-ethyl-5-phenylhydantoin, both relative to phenytoin. 

Gas Chromatography-Mass Spectrometry. In plasma sensitivity lOng/ml for methoin and 50ng/ml for 5-ethyl-5-phenylhydantoin—W. Yonekawa and H. J. Kupferberg, J. Chromat., 1979, 7(55 Biomed. AppL, 5, 161-167. 

High Pressure Liquid Chromatography. In serum methoin and 5-ethyl-5-phenylhydantoin, sensitivity 1 pg/ml, UV detection—P. M. Kabra et al., J. analyt. Toxicol., 1978, 2, 127-133. In urine methoin and metabolites, UV detection—A. Kiipfer etal., J. Chromat., 1982, 252 Biomed. AppL, 21, 93-100. 

Half-life. Plasma half-life, after a single dose, methoin about 7 hours, 5-ethyl-5-phenylhydantoin about 95 hours the half-life of the metabolite decreases to about 72 hours during chronic treatment. 

Mephenytoin is demethylated to 5-ethyl-5-phenylhydantoin (Nirvanol), which is an active anticonvulsant. Mephenytoin binds to plasma protein to the extent of 40%, with an elimination half-life of 7 hours. Mephenytoin causes sedation, whereas phenytoin does not. The incidence of dose- and time-dependent side effects of mephenytoin is lower than that seen with phenytoin. On the other hand, the incidence of severe and fatal hypersensitivity reactions is far higher than that reported for phenytoin. Therefore, mephenytoin is not the first drug of choice. It is used for the treatment of tonic-clonic, simple partial, and complex partial seizures... 

Ethyl-5-phenylhydantoin dissolved in twice its weight of hydrazine hydrate, and refluxed 19 hrs. 3-amino-5-ethyl-5-phenylhydantoin. Y 51%. F. e. s. J. S. Davidson, Soc. 1964, 4646. 

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