From the Guidelines
The recommended loading dose of intravenous Dilantin (phenytoin) for adults is 18-20 mg/kg, as indicated in the most recent and highest quality study 1.
Key Considerations for Administration
- The dose should be administered at a maximum rate of 50 mg/minute to minimize the risk of cardiovascular complications.
- For a typical 70 kg adult, this translates to approximately 1260-1400 mg total.
- The medication should be administered in normal saline (not dextrose solutions, which can cause precipitation) through a large peripheral vein or central line.
- Continuous cardiac monitoring is essential during administration due to the risk of hypotension and cardiac arrhythmias, as noted in 1 and 1.
Monitoring and Maintenance
- Blood pressure should be monitored every 5-10 minutes during infusion.
- Following the loading dose, serum phenytoin levels should be checked 2 hours after completion to ensure therapeutic range (10-20 mcg/mL).
- Maintenance dosing typically begins 12 hours after the loading dose at 4-6 mg/kg/day divided into 2-3 doses, although specific guidance on maintenance dosing is not provided in the referenced studies 1.
Adverse Effects
- Phenytoin administration is associated with several adverse effects, including soft tissue injury with extravasation, hypotension, cardiac dysrhythmias, and purple glove syndrome, as outlined in 1.
- It is crucial to be aware of these potential adverse effects to provide appropriate care and monitoring.
From the FDA Drug Label
The drug should be injected slowly intravenously at a rate not exceeding 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower. In adults, a loading dose of 10 to 15 mg/kg should be administered slowly A loading dose of 15 to 20 mg/kg of Phenytoin Sodium Injection intravenously will usually produce serum concentrations of phenytoin within the generally accepted serum total concentrations between 10 and 20 mcg/mL (unbound phenytoin concentrations of 1 to 2 mcg/mL)
The recommended IV Dilantin loading dose is:
- 10 to 15 mg/kg in adults 2
- 15 to 20 mg/kg in pediatric patients 2 The rate of administration should not exceed 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower 2.
From the Research
Intravenous Dilantin Loading Dose
The recommended dosage and administration guidelines for an intravenous (IV) Dilantin (phenytoin) loading dose are as follows:
- The total dose of IV phenytoin is typically 18 mg/kg, administered as a solution of 500 mg phenytoin in 50 mL normal saline using a constant infusion pump 3.
- The initial delivery rate can be 40 mg/min or 50 mg/min, depending on the patient's age and cardiovascular status 4, 3.
- For young patients, an infusion rate of 50 mg/min is reported to be safe 4.
- For older patients or those with cardiovascular co-morbidities, a slower infusion rate is recommended, with careful monitoring of heart rhythm and blood pressure 4.
- Therapeutic phenytoin blood levels (greater than 10 micrograms/mL) can be achieved in most patients using this loading dose regimen 3.
Administration Guidelines
- Cardiac rhythm should be monitored by telemetry, and rhythm strips and vital signs should be obtained every 15 minutes during infusion 3.
- Phenytoin levels should be monitored to avoid toxicity, and adjustments to the infusion rate or dose may be necessary 3, 5.
- Patients with renal function impairment may require adjusted dosing due to altered phenytoin binding 6.
Safety Considerations
- Rapid infusion rates (>50 mg/min) can increase the risk of cardiovascular adverse effects, including hypotension, arrhythmia, and cardiac arrest 4.
- Monitoring for adverse effects, such as burning at the IV infusion site, seizures, and changes in blood pressure, is essential during IV phenytoin administration 3, 5.