From the Guidelines
Phenytoin should be administered at a loading dose of 18-20 mg/kg intravenously, as indicated in the study published in the Annals of Emergency Medicine 1. The method of administration is crucial to avoid adverse effects, and the dose should be given slowly at a maximum rate to minimize the risk of hypotension, cardiac dysrhythmias, and soft tissue injury with extravasation. Some key points to consider when administering phenytoin include:
- Using a large vein with normal saline solution to avoid precipitation and local irritation
- Monitoring the patient for adverse effects such as hypotension, cardiac arrhythmias, and purple glove syndrome
- Maintaining a therapeutic blood level range of 10-20 mcg/mL to ensure efficacy and minimize toxicity
- Considering dose adjustments in patients with hepatic impairment, as phenytoin is primarily metabolized in the liver, as noted in the study 1. It is essential to weigh the benefits and risks of phenytoin administration, particularly in emergency situations such as status epilepticus, where alternative treatments like valproate may be considered due to their faster administration and fewer adverse effects, as discussed in the study 1.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION Pediatric Dosage Initially, 5 mg/kg/day in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily. A recommended daily maintenance dosage is usually 4 to 8 mg/kg.
The recommended initial dose of Phenytoin for pediatric patients is 5 mg/kg/day, which can be divided into 2 or 3 doses. The maintenance dose is usually 4 to 8 mg/kg/day 2.
From the Research
Phenytoin Dosing
- The recommended dose of phenytoin per kg is not strictly defined, but studies suggest the following:
- A mean administered dose of 14.5 mg/kg was used in one study 3
- Patients who received a lower per kilogram dose (12.8 mg/kg) were more likely to have suboptimal trough free concentrations 3
- A dose of 16.3 mg/kg was associated with a greater likelihood of adequate concentrations 3
- A calculated average dose of 19.1 mg per kilogram of phenytoin was used in another study to achieve therapeutic plasma levels 4
Method of Administration
- Phenytoin can be administered orally or intraneously
- Oral loading doses of phenytoin can be divided into two to four increments given over 3 to 21 hours to achieve therapeutic plasma levels 4
- The method of administration may vary depending on the patient's condition and the clinical setting