Intravenous Valproate Dosing in Neonates

The loading dosage of intravenous valproate required to achieve a desired serum concentration in neonates is not known. Two neonates with seizures received loading doses of intravenous valproate over 30 minutes. Serum valproate concentrations were measured 45 minutes and 3 hours after initiation of the infusion. Both neonates had received phenobarbital and phenytoin before the loading infusions. In the first patient, a loading dose of intravenous valproate of 10 mg/kg increased the 45-minute postinfusion serum valproate concentration to 41 μg/mL with a 3-hour postinfusion serum valproate concentration of 33 μg/mL. In the second patient, a loading dose of 25 mg/kg increased the 45-minute postinfusion serum valproic acid concentration to 100 μg/mL with a 3-hour postinfusion serum valproic acid concentration of 78 μg/mL. We found that each 1 mg/kg of intravenous valproate increased the 45-minute and 3-hour postinfusion serum valproic acid concentrations by approximately 4 μg/mL and 3 μg/mL, respectively. We ...