Plasma concentrations of phenobarbital in mother and child after combined prenatal and postnatal administration for prophylaxis of hyperbilirubinemia.

Phenobarbital is known to reduce serum bilirubin concentration in the newborn infant, but optimal dosage is unknown. Ten pregnant women and their infants were given a standard regimen including prenatal maternal administration and postnatal administration to the infant during the first week of life. The plasma levels of phenobarbital in the infants were found to increase during the period of administration, and to remain high for many days beyond the period of hyperbilirubinemia. Optimal dose schedules for phenobarbital should be based both upon pharmacologic effects (including those other than bilirubin disposition) and upon the pharmacokinetic profile of the drug in the newborn infant.