PURPOSE: To assess the single-dose pharmacokinetics of levetiracetam and its major metabolite ucb L057 in infants and young children with epilepsy. METHODS: Eligible patients with a stable regimen of antiepileptic medications received a single oral dose of levetiracetam 20 mg/kg administered as a 10% oral solution followed by a 24-hour pharmacokinetic evaluation. RESULTS: Thirteen subjects (age 2.3-46.2 months) enrolled and received levetiracetam; 12 provided evaluable pharmacokinetic data. Levetiracetam was rapidly absorbed and reached peak plasma concentration (t(max)) 1.4 +/- 0.9 hours after dosing. The mean half-life (t(1/2)) of levetiracetam was 5.3 +/- 1.3 hours, and the apparent clearance was 1.46 +/- 0.42 mL/min/kg. Graphical differences were observed among three age subgroups (1 to <6 months, 6 to <24 months, and 24 to <48 months); however, statistical analysis was limited due to each subgroup's small sample size. No significant gender differences were detected. Treatment-emergent adverse events were seen in three patients (23.1%) but were not considered to be related to levetiracetam. CONCLUSIONS: The mean t(1/2) of levetiracetam was shorter and its apparent clearance was more rapid for infants and young children than that previously reported for adults. When determining dosage, age-dependent drug clearance should be considered; these findings suggest that a larger dose of levetiracetam (corrected for body weight) needs to be considered for infants and young children with epilepsy than that given to adults with epilepsy. A single dose of levetiracetam was well tolerated in this study population.