Phenobarbital Pharmacokinetics in Neonates.

Phenobarbital (PB) pharmacokinetics were studied in order to find the optimal intravenous dose for neonatal convulsion. The subjects consisted of twenty-nine neonates (17males and 12 females) with seizure or intraventricular hemorrhage or asphyxia at birth.The mean gestational age and birth weight of the subjects were 37 weeks and 2.61 kg. The subjects over1, 000 g received 10 to 20 mg/kg of PB, and blood samples for assay of PB serum concentration were collected several times for one week after the intravenous administration. Pharmacokinetic parameters of one-compartment model for i. v. were calculated in each subject and compared with the results of laboratory examination.Twenty-one (95%) in twenty-two subjects who received single intravenous injection of 20mg/ kg PB showed serum concentration over 15, ug/ml within 6 hours after the administration.The i.v.dose of 20mgfkg was considered to be enough to protect neonatal convulsion. Calculated volume of disribution index (Vd) and elimination constant (Ke) were 0.924 +/0.247 (mean +/-SD) 1/kg and0.00512+/-0.00297 1/hr, respectively. There were positive correlation between total volume of distribution and body weight and negative one between Ke and serum creatinine concentration or blood urea nitrogen.