Table of contents

  • Brand Names
  • Chemistry
  • Pharmacologic Category
  • Mechanism of Action
  • Therapeutic Use
  • Pregnancy and Lactation Implications
  • Contraindications
  • Warnings and Precautions
  • Adverse Reactions
  • Toxicological Effects
  • Caution and personalized dose adjustment in patients with the following genotypes
  • Substrate of
  • Induces
  • Drug Interactions
  • Nutrition/Nutraceutical Interactions
  • Dosage
  • Pharmacokinetics and Pharmacodynamics
  • Special Considerations

Brand Names


Denmark: Pro-Epanutin; Finland: Pro-Epanutin; France: Prodilantin; Greece: Pro-Epanutin; Ireland: Pro-Epanutin; Sweden: Pro-Epanutin; UK: Pro-Epanutin.

North America

Canada: Cerebyx; USA: Cerebyx, Fosphenytoin.

Drug combinations


Fosphenytoin Sodium: C~16~H~13~N~2~Na~2~O~6~P. Mw: 406.24. (1) 2,4-Imidazolidinedione, 5,5-diphenyl-3-[(phosphonooxy)methyl]-, disodium salt; (2) 3-(Hydroxymethyl)-5,5-diphenylhydantoin, disodium phosphate. CAS-92134-98-0; CAS-93390-81-9 (fosphenytoin)(1993).

Pharmacologic Category

Anticonvulsants; Hydantoins. (ATC-Code: N03AB05).

Mechanism of action

Diphosphate ester salt of phenytoin which acts as a water-soluble prodrug of phenytoin. After administration, plasma esterases convert fosphenytoin to phosphate, formaldehyde, and phenytoin as active moiety. Phenytoin works by stabilizing neuronal membranes and decreasing seizure activity by increasing efflux or decreasing influx of sodium ions across cell membranes in motor cortex during generation of nerve impulses.

Therapeutic use

Used for short-term (up to 5 days) parenteral therapy (I.V. infusion or I.M. injection) when usual means of phenytoin administration is unavailable, inappropriate, or deemed less advantageous. Fosphenytoin is used for treatment of generalized convulsive status epilepticus. Can also be used for prevention and treatment of seizures occurring during neurosurgery and as short-term parenteral replacement for oral phenytoin.

Pregnancy and lactiation implications

Fosphenytoin is embryotoxic and teratogenic in animals. Phenytoin may cause fetal harm in pregnant women. Due to altered pharmacokinetics of phenytoin during pregnancy, increased frequency of seizures may occur in pregnant women receiving fosphenytoin.

Unlabeled use


Known hypersensitivity to fosphenytoin or any component of the formulation, phenytoin, or other hydantoins. Sinus bradycardia, sinoatrial block, second- or third-degree atrioventricular block, Adams-Stokes syndrome (Stokes-Adams disease).

Warnings and precautions

Administration of phenytoin associated with atrial and ventricular conduction depression and ventricular fibrillation. Hematologic effects (e.g. neutropenia, leukopenia, thrombocytopenia, pancytopenia, and anemias) reported with use (patients with previous history of adverse hematologic reaction to any drug may be at increased risk). Severe dermatologic reactions (including toxic epidermal necrolysis and Stevens-Johnson syndromes), might occur, and may be fatal. Acute hepatotoxicity associated with a hypersensitivity syndrome characterized by fever, skin eruptions, and lymphadenopathy reported to occur within first 2 months of treatment. Hypotension might occur, especially after I.V. administration at high doses and high rates of administration. Use with caution in hypotension, diabetes mellitus, fever, hepatic impairment, hypoalbuminemia, hypothyroidism, porphyria, or renal impairment. Effects with other sedative drugs or ethanol may be potentiated.



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