Mephenytoin (marketed as Mesantoin by Novartis) is a hydantoin, used as an anticonvulsant. It was introduced approximately 10 years after phenytoin, in the late 1940s. The significant metabolite of mephenytoin is nirvanol (5-ethyl-5-phenylhydantoin), which was the first hydantoin (briefly used as a hypnotic). However, nirvanol is quite toxic and mephenytoin was only considered after other less toxic anticonvulsants had failed. It can cause potentially fatal blood dyscrasia in 1% of patients.

Mephenytoin
Structural formula of mephenytoin
Space-filling model of the mephenytoin molecule
Clinical data
AHFS/Drugs.comMicromedex Detailed Consumer Information
MedlinePlusa611020
Routes of
administration
Oral
ATC code
Pharmacokinetic data
MetabolismCYP2C19
Elimination half-life7 hours
Identifiers
  • 5-Ethyl-3-methyl-5-phenyl-imidazolidine-2,4-dione
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.012 Edit this at Wikidata
Chemical and physical data
FormulaC12H14N2O2
Molar mass218.256 g·mol−1
3D model (JSmol)
  • O=C2N(C(=O)NC2(c1ccccc1)CC)C
  • InChI=1S/C12H14N2O2/c1-3-12(9-7-5-4-6-8-9)10(15)14(2)11(16)13-12/h4-8H,3H2,1-2H3,(H,13,16) checkY
  • Key:GMHKMTDVRCWUDX-UHFFFAOYSA-N checkY
  (verify)

Mephenytoin is no longer available in the US or the UK. It is still studied largely because of its interesting hydroxylation polymorphism.

References

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  • Shorvon SD, Fish DR, Perucca E, Dodson WE, eds. (2004). The Treatment of Epilepsy. Blackwell Publishing. ISBN 0-632-06046-8.
  • Resor SR (1991). The Medical Treatment of Epilepsy. Marcel Dekker. ISBN 0-8247-8549-5.
  • "Mephenytoin". The Comparative Toxicogenomics Database.