Phenobarbital maintenance dose requirements in treating neonatal seizures.

We studied the pharmacokinetics of phenobarbital in 15 neonates after a single intramuscular dose. The mean apparent distribution volume, half-life, and apparent total body clearance were 0.81 liter per kilogram, 103.4 hours, and 6.4 ml per hour per kilogram, respectively. Substantial interpatient variation was observed in the half-life and apparent total body clearance. Maintenance doses of 3.1 and 3.8 mg per kilogram per day were projected from the mean apparent total body clearance to produce plasma concentrations of 20 and 25 micrograms per milliliter, respectively. These recommendations provide initial maintenance dosage guidelines, which should be adjusted according to plasma concentrations and clinical effects.