Efficacy of phenobarbital monotherapy in treatment of neonatal seizures -- relationship to blood levels.

Seventy-one neonates were observed for the relationship between phenobarbital plasma concentrations and elimination of seizures. Sixty neonates (85%) had seizures controlled by phenobarbital alone. Effective plasma concentrations were 10.1 to 46.4 mg per liter. Although 36 neonates had seizures controlled by phenobarbital concentrations below 20 mg per liter, 7 neonates required levels above 30 mg per liter. We recommend that plasma phenobarbital concentrations should equal or surpass 40 mg per liter before additional anticonvulsants are used for neonates with seizures.