Urinary excretion of phenobarbital in a neonate having withdrawal symptoms.

Utilizing methods of gas chromatography-mass spectrometry-computer systems operated in a chemical ionization mode, metabolites of mephobarbital were demostrated in urines collected from two infants whose mother was treated with mephobarbital during pregnancy. Identification of the major metabolite in one infant was possibe for 22 days after delivery. The urinary half-life of mephobartial was 30 hours and the half-life of phenobarbital was 48 hours. Both infants demonstrated withdrawal symptoms for four to six months and manifested the physical phenotype of infants exposed in utero to anticonvulsant agents.