Phenytoin kinetics in children.

Previous studies have shown the importance of phenytoin kinetics in the management of adult patients with seizure disorders. The long half-life in adults makes single daily dosing realistic in terms of blood levels and anticonvulsant effectiveness. This report shows a wide range in both half-lives and volumes of distribution of phenytoin in 11 children (ages 6 months to 6 years) with seizure disorders. Ten of these patients have very short phenytoin half-lives (1.2 to 6.7 hours). The data strongly suggest that current recommendations for phenytoin dosage regimens in adults cannot necessarily be used in children. Blood levels must be followed closely in this age group to determine the required dosage and dose interval.