Fosphenytoin — Membership Pricing

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About Fosphenytoin

Fosphenytoin is a vital medication used to rapidly control and prevent certain types of seizures, especially in emergency situations or when oral administration is not feasible. Understanding its function and potential costs is crucial. TheDrugClub is committed to helping members manage their prescription expenses, offering avenues for potential savings on essential medications like fosphenytoin.

Fosphenytoin is an anticonvulsant medication primarily used in the acute management of generalized tonic-clonic status epilepticus, a severe and life-threatening form of seizure. It's also utilized for the prevention and treatment of seizures during neurosurgery, or when oral phenytoin (its parent drug) is not an option due to patient condition or absorption issues.

How Fosphenytoin Works

Fosphenytoin is a prodrug of phenytoin, meaning it's an inactive compound that converts into the active drug (phenytoin) within the body after administration. Once converted, phenytoin works by stabilizing neuronal membranes and reducing seizure activity. It achieves this by prolonging the inactive state of voltage-gated sodium channels in the brain, thereby limiting the rapid firing of neurons that causes seizures. Unlike oral phenytoin, fosphenytoin can be administered intravenously (IV) or intramuscularly (IM), offering a faster onset of action and better tolerability at the injection site.

Typical Costs of Fosphenytoin

As a specialized, injectable medication often used in emergency or hospital settings, fosp

The information above is for educational purposes only and does not constitute medical advice. Consult your healthcare provider before making medication decisions.

What Fosphenytoin is approved for (FDA label)

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 (2.4) and Warnings and Precautions (5.2) ] . 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, as short-term use, for oral phenytoin. Fosphenytoin sodium injection should be used only when oral phenytoin administration is not possible. ( 1 )

Source: Read the full FDA label on DailyMed. Label effective date: February 18, 2026.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Boxed warning for Fosphenytoin (FDA label)

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 toxicity increases with infusion rates above the recommended infusion rate, these events have also been reported at or below the recommended infusion rate. Reduction in rate of administration or discontinuation of dosing may be needed [see Dosage and Administration ( 2.3 , 2.4 ) and Warnings and Precautions ( 5.2 )]. WARNING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION RATES See full prescribing information for complete boxed warning. • The rate of intravenous fosphenytoin sodium 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. • Reduction in rate of administration or discontinuation of dosing may be needed ( 2.3 , 2.4 , 5.2 ) .

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Dosage forms and strengths for Fosphenytoin (FDA label)

Fosphenytoin sodium Injection, USP is a clear, colorless to pale yellow solution available as 50 mg phenytoin sodium equivalents (PE) per mL in: • 10 mL single-dose injection vials, each containing 500 mg PE/10 mL (50 mg PE/mL) • 2 mL single-dose injection vials, each containing 100 mg PE/2 mL (50 mg PE/mL) Injection: 50 mg phenytoin sodium equivalents (PE)/mL available as: • 10 mL single-dose injection vials, each containing 500 mg PE/10mL (50 mg PE/mL) ( 3 ) • 2 mL single-dose injection vials, each containing 100 mg PE/2 mL (50 mg PE/mL) ( 3 )

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Adverse reactions for Fosphenytoin (FDA label)

The following serious adverse reactions are described elsewhere in the labeling: • Cardiovascular Risk Associated with Rapid Infusion [see Warnings and Precautions (5.2) ] • Withdrawal Precipitated Seizure, Status Epilepticus [see Warnings and Precautions (5.3) ] • Serious Dermatologic Reactions [see Warnings and Precautions (5.4) ] • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see Warnings and Precautions (5.5) ] • Hypersensitivity [see Warnings and Precautions (5.6) ] • Angioedema [see Warnings and Precautions (5.7) ] • Hepatic Injury [see Warnings and Precautions (5.8) ] • Hematopoietic Complications [see Warnings and Precautions (5.9) ] • Sensory Disturbances [see Warnings and Precautions (5.10) ] • Local Toxicity (Including Purple Glove Syndrome) [see Warnings and Precautions (5.11) ] • Exacerbation of Porphyria [see Warnings and Precautions (5.14) ] • Teratogenicity and Other Harm to the Newborn [see Warnings and Precautions (5.15) ] • Hyperglycemia [see Warnings and Precautions (5.16) ] Most common adverse reactions (incidence ≥10%) are: • Adults: pruritus, nystagmus, dizziness, somnolence, and ataxia • Pediatrics : vomiting, nystagmus, and ataxia ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Glenmark Pharmaceuticals Inc., USA at 1 (888) 721-7115 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Contraindications for Fosphenytoin (FDA label)

Fosphenytoin sodium is contraindicated in patients with: • A history of hypersensitivity to fosphenytoin sodium injection or its inactive ingredients, or to phenytoin or other hydantoins [see Warnings and Precautions (5.6) ] . Reactions have included angioedema. • Sinus bradycardia, sino-atrial block, second and third degree A-V block, or Adams-Stokes syndrome because of the effect of parenteral phenytoin or fosphenytoin sodium on ventricular automaticity. • A history of prior acute hepatotoxicity attributable to fosphenytoin sodium or phenytoin [see Warnings and Precautions (5.8) ] . • Coadministration with delavirdine because of the potential for loss of virologic response and possible resistance to delavirdine or to the class of non-nucleoside reverse transcriptase inhibitors.

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Warnings and precautions for Fosphenytoin (FDA label)

• Dosing Errors: Do not confuse the amount of drug to be given in PE with the concentration of the drug in the vial. Ensure the appropriate volume is withdrawn from the vial when preparing for administration. ( 5.1 ) • Withdrawal Precipitated Seizure: May precipitate status epilepticus. Dose reductions or discontinuation should be done gradually. ( 5.3 ) • Serious Dermatologic Reactions: Discontinue at the first sign of a rash, unless clearly not drug-related. If signs or symptoms suggest SJS/TEN, fosphenytoin sodium should not be resumed; consider alternative therapy. ( 5.4 ) • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity: If signs or symptoms of hypersensitivity are present, evaluate the patient immediately.

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.

Drug interactions for Fosphenytoin (FDA label)

Fosphenytoin is extensively bound to human plasma proteins. Drugs highly bound to albumin could increase the unbound fraction of fosphenytoin. Although, it is unknown whether this could result in clinically significant effects, caution is advised when administering fosphenytoin sodium with other drugs that significantly bind to serum albumin. The most significant drug interactions following administration of fosphenytoin sodium are expected to occur with drugs that interact with phenytoin. Phenytoin is extensively bound to serum plasma proteins and is prone to competitive displacement. Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19 and is particularly susceptible to inhibitory drug interactions because it is subject to saturable metabolism. Inhibition of metabolism may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity. Monitoring of phenytoin serum levels is recommended when a drug interaction is suspected.

Source: FDA prescribing information (DailyMed). Set ID: a0def32c-e693-43e5-9509-0cef9642441c. SPL document ID: 18a83af7-61ff-4fc0-9c52-093422e21781. Label effective date: February 18, 2026. Read the full label.

Excerpt from the FDA-approved prescribing information. This is not medical advice; talk to your doctor or pharmacist.