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Data updated: Mar 29, 2026

FOSPHENYTOIN SODIUM

FOSPHENYTOIN SODIUM
Neurology Approved 2007-08-06

Fosphenytoin sodium is an injectable medication indicated for the treatment of generalized tonic-clonic status epilepticus. It is also used for the prevention and treatment of seizures in patients undergoing neurosurgery. Additionally, the drug serves as a short-term substitute for oral phenytoin when oral administration is not possible.

Source: FDA Label • Hikma

How FOSPHENYTOIN SODIUM Works

Fosphenytoin is a prodrug that is converted into phenytoin to exert its anticonvulsant effects. It is thought to work through the voltage-dependent blockade of sodium channels in neuronal membranes. This action results in a reduction of sustained high-frequency neuronal discharges, which helps stabilize electrical activity in the brain.

6
Indications
--
Phase 3 Trials
18
Years on Market

Details

Status
Prescription
First Approved
2007-08-06
Routes
INJECTION
Dosage Forms
INJECTABLE

FOSPHENYTOIN SODIUM Approval History

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What FOSPHENYTOIN SODIUM Treats

3 indications

FOSPHENYTOIN SODIUM is approved for 3 conditions since its original approval in 2007. These indications span multiple therapeutic areas including oncology, immunology, and more.

  • Generalized tonic-clonic status epilepticus
  • Prevention and treatment of seizures occurring during neurosurgery
  • Short-term substitution for oral phenytoin when oral administration is not possible
Source: FDA Label

FOSPHENYTOIN SODIUM Boxed Warning

CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION RATES The rate of intravenous fosphenytoin sodium injection administration should not exceed 150 mg phenytoin sodium equivalents (PE) per minute in adults and 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) in pediatric patients because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous fosphenytoin sodium injection. Although the risk of cardiovascular...

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Understanding FDA Approval Types
Count Type What it means
- ORIG Original approval - drug first enters market
- SUPPL - Efficacy New indication (new disease/condition approved)
- SUPPL - Labeling Label text changes (warnings, dosing updates)
- SUPPL - Manufacturing Production changes (new facility)
- SUPPL - Chemistry Formulation changes (new dosage strength)

Green lines in the timeline show ORIG and Efficacy approvals - the clinically meaningful milestones.

FOSPHENYTOIN SODIUM FDA Label Details

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Indications & Usage

FDA Label (PDF)

Fosphenytoin sodium injection is indicated for the treatment of generalized tonic-clonic status epilepticus and prevention and treatment of seizures occurring during neurosurgery. Fosphenytoin sodium injection can also be substituted, short-term, for oral phenytoin. Fosphenytoin sodium injection should be used only when oral phenytoin administration is not possible [see Dosage and Administration and Warnings and Precautions ] . Fosphenytoin sodium injection is indicated for the treatment of generalized tonic-clonic status epilepticus and prevention and treatment of seizures occurring during ne...

⚠️ BOXED WARNING

WARNING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION RATES The rate of intravenous fosphenytoin sodium injection administration should not exceed 150 mg phenytoin sodium equivalents (PE) per minute in adults and 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) in pediatric patients beca...

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Data Sources

Data sourced from official FDA and NIH databases. Click links to verify on original sources.