Abstract
Transplacental and elimination pharmacokinetics of phenobarbital (PB) were analyzed in pregnant women and their neonates with the aim of determining the dose to be administered to pregnant women to achieve levels in the neonate for prevention of neonatal intracerebral hemorrhage (ICH). A single PB dose of 500 mg was selected to achieve a serum concentration of 10 μg/mL in the women according to the equation: dose (mg/Kg) = serum cone (μg/ mL) x Vd (L/Kg); assuming average weight to be 50 Kg and Vd =1.0 L/Kg. Twenty-five women in premature labor <35 wks gestation received 500 mg PB administered intravenously over 30 min. Average weight of the women was 69.1 ± 13.5 Kg (all values mean ± SD); the actual mean dose of PB therefore was 7.5 ± 1.4 mg/Kg. The mean time from PB administration to delivery was 5.6 ± 4.6 hrs (range 16 min. to 17 hrs). The maternal serum PB level at delivery was 8.8 ± 1.2 ug/mL and the cord serum level was 9.0 ± 1.8 μg/mL. There was no correlation between the time from PB administration to delivery and the cord:maternal serum concentration ratio. This indicated transplacental equilibration within 16 min. of maternal dosing. Mean apparent th of PB estimated in 11 infants was 175.5 ± 45.6 hrs; this is comparable with th in neonates receiving PB postnatally. Based on this study, we recommend a 10 mg/Kg dose of PB for the pregnant woman to achieve a level of 10 pg/ml. This level has been found to be protective against ICH (Shankaran et al, Ann Neurol Abstr #14, 1984).
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Shankaran, S., Cepeda, E., Ilagan, N. et al. 414 PHARMACOKINETIC BASIS FOR ANTENATAL DOSING OF PHENOBARBITAL FOR THE PREVENTION OF NEONATAL INTRACERE BRRL HEMORRHAGE. Pediatr Res 19, 179 (1985). https://doi.org/10.1203/00006450-198504000-00444
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DOI: https://doi.org/10.1203/00006450-198504000-00444