Title: Fosphenytoin
CAS Registry Number: 93390-81-9
CAS Name: 5,5-Diphenyl-3-[(phosphonooxy)methyl]-2,4-imidazolidinedione
Additional Names: 3-(hydroxymethyl)-5,5-diphenylhydantoin phosphate ester; (3-phosphoryloxymethyl)phenytoin; prophenytoin
Molecular Formula: C16H15N2O6P
Molecular Weight: 362.27
Percent Composition: C 53.05%, H 4.17%, N 7.73%, O 26.50%, P 8.55%
Literature References: Prodrug of phenytoin, q.v. Prepn: V. J. Stella, K. B. Sloan, US 4260769 (1981 to INTERx). Series of articles on chemical properties and pharmacokinetics: S. A. Varia et al., J. Pharm. Sci. 73, 1068-1090 (1984). Pharmacology: R. D. Smith et al., Epilepsia 30, Suppl. 2, S15 (1989). Clinical bioavailablilty and pharmacokinetics: B. D. Jamerson et al., ibid. 31, 592 (1990). Series of articles on use in epilepsy: Neurology 46, Suppl. 1, S1-S28 (1996). Clinical trial in epilepsy and neurosurgery: B. J. Wilder et al., Arch. Neurol. 53, 764 (1996).
Properties: White crystals from acetone, mp 173-176.5°.
Melting point: mp 173-176.5°
Derivative Type: Disodium salt
CAS Registry Number: 92134-98-0
Additional Names: Fosphenytoin sodium
Manufacturers' Codes: ACC-9653
Trademarks: Cerebyx (Pfizer); Pro-Epanutin (Pfizer)
Molecular Formula: C16H13N2Na2O6P
Molecular Weight: 406.24
Percent Composition: C 47.30%, H 3.23%, N 6.90%, Na 11.32%, O 23.63%, P 7.62%
Properties: White crystals as the dihydrate from water-ethanol-acetone, mp 220° (softens). pH of a saturated aqueous soln: ~9. Soly at 25° (mg/ml): 142 in water. LD50 in mice, rats (mg/kg): 234, 363 i.v. (Smith).
Melting point: mp 220° (softens)
Toxicity data: LD50 in mice, rats (mg/kg): 234, 363 i.v. (Smith)
Therap-Cat: Anticonvulsant.
Keywords: Anticonvulsant.
Fospirate Fospropofol Fosthiazate Fosthietan Fotemustine

Systematic (IUPAC) name
(2,5-dioxo-4,4-diphenyl-imidazolidin-1-yl)methoxyphosphonic acid
Clinical data
Trade names Cerebyx
AHFS/ monograph
MedlinePlus a604036
Pregnancy cat. D (US)
Legal status Prescription only
Routes Intravenous, intramuscular
Pharmacokinetic data
Bioavailability 100% (IM)
Protein binding 95 to 99%
Metabolism Hepatic
Half-life 15 minutes to convert to phenytoin
Excretion Renal (as phenytoin)
CAS number 93390-81-9 YesY
ATC code N03AB05
PubChem CID 56339
DrugBank DB00252
ChemSpider 50839 YesY
UNII B4SF212641 YesY
KEGG D07993 YesY
Chemical data
Formula C16H15N2O6P 
Mol. mass 362.274 g/mol
 N (what is this?)  (verify)

Fosphenytoin (fosphenytoin sodium injection, previously Cerebyx, Parke-Davis; Prodilantin, Pfizer Holding France[1]) is a water-soluble phenytoin prodrug that is administered intravenously to deliver phenytoin, potentially more safely than intravenous phenytoin. It is most commonly used in the acute treatment convulsive status epilepticus.

On 18 November 2004, Sicor (a subsidiary of Teva) received a tentative approval letter from the United States Food and Drug Administration for a generic version of fosphenytoin.[2]