Home Drug Guide Fosphenytoin Sodium

Drug Guide

Generic Name

Fosphenytoin Sodium

Brand Names Cerebyx, Sesquient

Classification

Therapeutic: Anticonvulsant

Pharmacological: Prodrug of phenytoin, a hydantoin anticonvulsant

FDA Approved Indications

  • Prevention and treatment of seizures associated with epilepsy, status epilepticus

Mechanism of Action

Fosphenytoin is a prodrug that is rapidly converted into phenytoin in the body. Phenytoin stabilizes neuronal membranes and decreases neuronal excitability by blocking voltage-gated sodium channels.

Dosage and Administration

Adult: Initial: 10-20 mg PE/kg IV infusion at 150 mg PE/min; adjust as needed based on response and tolerability.

Pediatric: Same as adults; dosing is weight-based, typically 5-15 mg PE/kg.

Geriatric: Use with caution, starting at lower doses due to increased sensitivity and comorbidities.

Renal Impairment: Adjust dosing based on clinical response and tolerability.

Hepatic Impairment: Use with caution; monitor closely as metabolism may be affected.

Pharmacokinetics

Absorption: Rapidly distributes after IV administration; bioavailability not applicable.

Distribution: Widely distributed across body tissues; crosses the blood-brain barrier.

Metabolism: Converted to phenytoin in the body.

Excretion: Primarily renal; small amount excreted unchanged.

Half Life: Approx. 8-15 hours for fosphenoytin, variable depending on conversion and clearance.

Contraindications

  • Hypersensitivity to fosphenoytin or phenytoin.

Precautions

  • Use cautiously in patients with heart block, sinus bradycardia, or Adams-Stokes syndrome.
  • Monitor for hypotension, arrhythmias during IV infusion.
  • Use in pregnancy only if clearly needed; potential teratogenicity known.

Adverse Reactions - Common

  • Hypotension (Common)
  • Headache (Common)
  • Nausea/vomiting (Common)
  • Rash (Common)

Adverse Reactions - Serious

  • Arrhythmias, including bradycardia and ventricular fibrillation (Serious)
  • Stevens-Johnson syndrome, toxic epidermal necrolysis (Rare)
  • Hypersensitivity reactions, including anaphylaxis (Rare)

Drug-Drug Interactions

  • Other CNS depressants, warfarin, hormonal contraceptives, carbamazepine, valproic acid.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor neurological status, vital signs, cardiac rhythm, skin for hypersensitivity, and serum levels of phenytoin if applicable.

Diagnoses:

  • Risk for hypotension or arrhythmias during infusion.
  • Risk for allergic reaction.

Implementation: Administer via IV infusion, keep rate within recommended limits. Monitor infusion site for phlebitis.

Evaluation: Assess for seizure control and adverse effects.

Patient/Family Teaching

  • Report signs of allergic reactions, rash, or changes in heart rhythm.
  • Inform that blood levels of phenytoin may need monitoring.
  • Advise on avoiding other CNS depressants unless prescribed.

Special Considerations

Black Box Warnings:

  • SERIOUS DERMATOLOGIC REACTIONS: Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported.
  • CARDIAC ARREST, HYPOTENSION, AND OTHER OUTCOMES CAN OCCUR WHEN FOSPHENYTOIN IS ADMINISTERED IV. Proper infusion rates must be followed.

Genetic Factors: Genetic variations affecting metabolism may influence drug levels and response.

Lab Test Interference: May interfere with serum folate and vitamin levels.

Overdose Management

Signs/Symptoms: Ataxia, nystagmus, dizziness, coma, hypotension, arrhythmias.

Treatment: Discontinue drug, provide supportive care, monitor cardiac function, administer sedation if needed, and consider activated charcoal if ingestion was recent.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable under recommended storage conditions.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.