Mephenytoin

{{short description|Chemical compound}}

{{Drugbox

| Watchedfields = changed

| verifiedrevid = 459493896

| IUPAC_name = 5-Ethyl-3-methyl-5-phenyl-imidazolidine-2,4-dione

| image = Mephenytoin.svg

| alt = Structural formula of mephenytoin

| width = 135

| image2 = Mephenytoin 3D spacefill.png

| alt2 = Space-filling model of the mephenytoin molecule

| width2 = 160

| tradename =

| Drugs.com = {{drugs.com|CONS|mephenytoin}}

| MedlinePlus = a611020

| pregnancy_US = C

| legal_status =

| routes_of_administration = Oral

| bioavailability =

| metabolism = CYP2C19

| elimination_half-life = 7 hours

| excretion =

| IUPHAR_ligand = 7223

| CAS_number_Ref = {{cascite|correct|??}}

| CAS_number = 50-12-4

| ATC_prefix = N03

| ATC_suffix = AB04

| ATC_supplemental=

| PubChem = 4060

| DrugBank_Ref = {{drugbankcite|correct|drugbank}}

| DrugBank = DB00532

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 3920

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = R420KW629U

| KEGG_Ref = {{keggcite|correct|kegg}}

| KEGG = D00375

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 861

| C=12 | H=14 | N=2 | O=2

| smiles = O=C2N(C(=O)NC2(c1ccccc1)CC)C

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 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)

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = GMHKMTDVRCWUDX-UHFFFAOYSA-N

}}

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