Phenytoin Dosing in Infants a Report of three Cases

Abstract

Three case reports indicate that infants below 10 kg in weight require greater mg/kg doses of phenytoin than larger infants or adults in order to achieve therapeutic plasma levels between 10–20 mcg/ml. In the absence of access to plasma phenytoin assay services, alternative drug therapy would usually be considered when a dose of 8 mg/kg/day of phenytoin fails to prevent seizures. These case reports reinforce the need to monitor the plasma phenytoin level when the clinical response to normal doses is inadequate. The correlation of infant to adult doses agrees well when doses are based on body surface area rather than on body weight.