• Molecular NameMephenytoin
  • SynonymMephentoin; Methyl Hydantoin; Methylphenetoin
  • Weight218.256
  • Drugbank_IDDB00532
  • ACS_NO50-12-4
  • Show 3D model
  • LogP (experiment)1.69
  • LogP (predicted, AB/LogP v2.0)1.7
  • pka8.1
  • LogD (pH=7, predicted)1.67
  • Solubility (experiment)1270 mg/L
  • LogS (predicted, ACD/Labs)(ph=7)-1.93
  • LogSw (predicted, AB/LogsW2.0)1.65
  • Sw (mg/ml) (predicted, ACD/Labs)2.4
  • No.of HBond Donors1
  • No.of HBond Acceptors4
  • No.of Rotatable Bonds2
  • TPSA49.41
  • StatusFDA approved
  • AdministrationN/A
  • PharmacologyA hydantoin, used as an anticonvulsant.
  • Absorption_valueN/A
  • Absorption (description)Rapidly absorbed after oral administration.
  • Caco_2N/A
  • BioavailabilityN/A
  • Protein binding40.0
  • Volume of distribution (VD)N/A
  • Blood/Plasma Partitioning ratio (D_blood)N/A
  • MetabollsmDuring chronic administration, the major metabolite is 5-ethyl-5-phenylhydantoin (nirvanol) which is a more active anticonvulsant than mephenytoin and accounts for at least 22% of the daily dose in the 24-h urine. After a single dose, the major metabolite is 4′-hydroxymethoin which is excreted in the urine as a glucuronide conjugate and accounts for 43% of a dose in 24 h; only about 1% of a single dose is excreted in the urine as 5-ethyl-5-phenylhydantoin; 5-ethyl-5-(4-hydroxyphenyl)-hydantoin has also been detected in the urine in both free and conjugated forms, together with minor amounts of other conjugated hydroxy metabolites; very little unchanged drug is excreted in the urine.
  • Half lifeafter a single dose, mephenytoin about 7 h, 5-ethyl-5-phenylhydantoin about 95 h; the half-life of the metabolite decreases to about 72 h during chronic treatment.
  • ExcretionN/A
  • Urinary ExcretionN/A
  • CleranceN/A
  • ToxicityThe estimated minimum lethal dose is 5 g. Mephenytoin gives rise to toxic symptoms more frequently than phenytoin and cases of fatal aplastic anaemia have been reported; the toxicity of the drug is attributed to the proven toxicity of 5-ethyl-5-phenylhydantoin. Acute overdosage may result in coma.
  • LD50 (rat)N/A
  • LD50 (mouse)N/A