What is the loading dose of Phenytoin for Status Epilepticus?

From the Guidelines

The loading dose of phenytoin for status epilepticus is 18-20 mg/kg, as indicated in the most recent and highest quality study 1. This dose should be administered intravenously, and the medication should be diluted in normal saline to avoid precipitation. The administration should be done with caution, monitoring for potential cardiovascular side effects such as hypotension and arrhythmias. Some key points to consider when administering phenytoin for status epilepticus include:

• The dose should not exceed 20 mg/kg, as higher doses may increase the risk of adverse effects 1.
• The medication should be administered at a maximum rate of 50 mg/minute to minimize the risk of cardiovascular complications.
• Blood pressure and cardiac rhythm should be monitored during administration, and the rate of infusion should be reduced if the heart rate decreases by 10 beats per minute.
• The therapeutic serum level goal is 10-20 mcg/mL, and serum phenytoin levels should be monitored on an outpatient basis to ensure that the patient is maintaining a therapeutic level.
• For patients with hypersensitivity to phenytoin or those with certain cardiac conditions, fosphenytoin (a prodrug of phenytoin) may be used instead at an equivalent dose, as it can be administered more rapidly and with fewer infusion-related complications 1.

From the FDA Drug Label

In adults, a loading dose of 10 to 15 mg/kg should be administered slowly intravenously, at a rate not exceeding 50 mg per minute (this will require approximately 20 minutes in a 70-kg patient). The loading dose should be followed by maintenance doses of 100 mg orally or intravenously every 6 to 8 hours In the pediatric population, a loading dose of 15 to 20 mg/kg of phenytoin sodium 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 loading dose of Phenytoin for Status Epilepticus is:

• 10 to 15 mg/kg in adults, administered slowly intravenously at a rate not exceeding 50 mg per minute.
• 15 to 20 mg/kg in pediatric patients, administered slowly intravenously at a rate not exceeding 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower 2.

From the Research

Phenytoin Loading Dose for Status Epilepticus

• The loading dose of Phenytoin for Status Epilepticus is typically administered intravenously to rapidly achieve therapeutic levels 3.
• A study published in 2024 found that a higher median weight-based loading dose of 19.1 mg/kg was a predictor of achieving the corrected goal level of ≥10 mcg/mL after the initial load 3.
• Another study from 2003 used a loading dose of 18 mg/kg infused over 20 min, followed by a maintenance dose of 2.5 mg/kg every 12 hours 4.
• A 1981 study used a loading dose of 15 mg/kg in 100 ml of 0.9% sodium chloride injection, infused at 30-50 mg/min, to achieve therapeutic serum concentrations within 5-30 minutes 5.
• The American Academy of Neurology and other guidelines have traditionally recommended a loading dose of 15-20 mg/kg, although the optimal dose may vary depending on individual patient factors 6, 7.

Comparison with Other Antiepileptic Drugs

• Some studies suggest that levetiracetam may be preferred over phenytoin for the treatment of status epilepticus due to its easier administration and lower risk of adverse effects 6.
• Sodium valproate has also been compared to phenytoin in the treatment of status epilepticus, with some studies suggesting that valproate may have a higher tolerability and lower hemodynamic instability 7.

Administration and Monitoring

• Phenytoin loading doses should be administered with caution and monitored closely for adverse effects, such as local cutaneous reactions, hypotension, and cardiac arrhythmias 3, 4, 5.
• Blood samples should be drawn regularly to monitor phenytoin levels and adjust the dose as needed to achieve therapeutic concentrations 3, 5.