Fosphenytoin Dosage for Pediatric Status Epilepticus
For pediatric status epilepticus, fosphenytoin should be administered at a loading dose of 15-20 mg PE/kg at a rate not exceeding 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower). 1
Loading Dose Administration
- The recommended loading dose for pediatric status epilepticus is 15-20 mg PE/kg 2, 1
- Maximum infusion rate should not exceed 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) to minimize cardiovascular adverse effects 1
- Continuous monitoring of ECG, blood pressure, and respiratory function is essential during administration 1
- Observe the patient throughout the period where maximal serum phenytoin concentrations occur (approximately 10-20 minutes after the end of infusion) 1
Maintenance Dosing
- Initial maintenance dose should be 2-4 mg PE/kg given 12 hours after the loading dose 1
- Subsequent maintenance dosing should be 4-8 mg PE/kg/day divided every 12 hours 1
- Maintenance infusion rate should not exceed 1-2 mg PE/kg/min (or 100 mg PE/min, whichever is slower) 1
- Subsequent maintenance doses should be individualized by monitoring serum phenytoin concentrations to achieve therapeutic levels 1
Important Administration Considerations
- Dilute fosphenytoin in 5% Dextrose Injection or 0.9% Sodium Chloride Injection to a concentration ranging from 1.5 to 25 mg PE/mL 1
- Maximum concentration of fosphenytoin in any solution should be 25 mg PE/mL 1
- Intramuscular administration should ordinarily not be used in pediatric patients with status epilepticus 1
- Therapeutic serum total phenytoin concentrations should be maintained between 10-20 mcg/mL (unbound phenytoin 1-2 mcg/mL) 1, 3
Monitoring and Safety
- Phenytoin concentrations should not be monitored until conversion to phenytoin is essentially complete (approximately 2 hours after IV infusion) 1
- Be prepared to provide respiratory support and monitor oxygen saturation throughout administration 4
- Watch for potential adverse effects including hypotension, bradycardia, and cardiac arrhythmias 5, 1
- A loading dose of 18-20 mg/kg typically achieves therapeutic levels in most pediatric patients 6, 3
Medication Errors Prevention
- Always express the dose, concentration, and infusion rate as phenytoin sodium equivalents (PE) 1
- Fatal errors have occurred when the concentration (50 mg PE/mL) was misinterpreted to mean the total content of the vial 1
- Ensure the appropriate volume of fosphenytoin is withdrawn when preparing doses 1
Alternative Treatments
- If fosphenytoin administration does not terminate seizures, consider other anticonvulsants 1
- Levetiracetam (30 mg/kg IV over 5 minutes) is an alternative second-line agent with fewer adverse effects and similar efficacy 2, 7
- Valproate (20-30 mg/kg IV over 5-20 minutes) is another second-line option with fewer hypotensive effects 2
Fosphenytoin's advantages over phenytoin include more convenient administration, faster infusion rates, and lower potential for adverse local reactions at injection sites 8. However, therapeutic drug monitoring is essential for optimal dosing in pediatric patients with status epilepticus 6.