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Phenobarbital prophylaxis for hyperbilirubinemia in preterm infants. A controlled study of bilirubin disappearance
Insights
Phenobarbital (PB) effectively reduces neonatal hyperbilirubinemia at higher doses (12 mg/kg), significantly increasing bilirubin clearance. However, these doses also increase quiet sleep in newborns, indicating a dose-dependent behavioral effect.
Area of Science:
- Neonatology
- Pharmacology
- Pediatric Medicine
Background:
- Phenobarbital (PB) is used for neonatal hyperbilirubinemia prophylaxis.
- Limited quantitative data exists on PB's efficacy and optimal dosing.
- Various dosing schedules have been proposed without clear evidence.
Purpose of the Study:
- To quantitatively evaluate the effects of phenobarbital on bilirubin disposition.
- To assess the impact of phenobarbital on neonatal behavior.
- To determine the relationship between PB dosage, bilirubin levels, and infant behavior.
Main Methods:
- A randomized, controlled trial involving 43 preterm infants.
- Infants received single doses of 0, 4, 8, or 12 mg/kg of PB.
- Bilirubin levels and infant behavior (via time-lapse filming) were monitored.
Main Results:
- Only the 12 mg/kg PB dose significantly increased the total serum bilirubin disappearance rate (p < 0.01) by postnatal day 7.
- Higher PB doses correlated with increased quiet sleep time (r = 0.61, p < 0.05).
- PB pharmacokinetics were consistent across doses and not correlated with gestational age.
Conclusions:
- Phenobarbital requires higher doses (≥12 mg/kg) to significantly enhance bilirubin clearance in newborns.
- These effective doses are associated with observable behavioral changes, specifically increased quiet sleep.
- Clinical use of PB for hyperbilirubinemia necessitates balancing efficacy with potential behavioral effects.
Abstract:
Phenobarbital (PB) has been used at several pediatric centers for prophylaxis against neonatal hyperbilirubinemia. However, few attempts have been made to evaluate this procedure quantitatively, and a variety of dose schedules has been proposed. Therefore, a randomized, controlled clinical trial was performed in which the effects on bilirubin disposition and on neonatal behavior was quantitated. Forty-three preterm infants were randomized into one of four dose groups and given 0, 4, 8, or 12 mg of PB per kg in a single dose within the first few hours after birth (mean 2.2 h). The total serum bilirubin disappearance rate was found to be significantly increased (p less than 0.01) only in the 12 mg/kg group. This effect was not evident until postnatal day 7. The 4 and 8 mg/kg groups were not significantly different from the control group at any time. Infant behavior was monitored by a non-invasive time-lapse filming technique. The time spent in quiet sleep was found to be proportional to the plasma PB concentration at one day of age (r = 0.61). The infants in the 12 mg group spent a larger proportion of time in quiet sleep than the other groups (p less than 0.05). The plasma half-lives, plasma clearances and volumes of distribution of PB were similar in the three dose groups. No correlation was found between the pharmacokinetics and the gestational age of the infant. It is concluded that in order to enhance the bilirubin disappearance rate, PB has to be administered in doses that will affect behavior.