Glucaric acid excretion as index of hepatic glucuronidation in neonates after phenobarbital treatment.

The urinary excretion of glucaric and glucuronic acid was investigated in neonates receiving phenobarbital intramuscularly or orally. Whereas there was no significant difference from the control-subjects in glucuronic acid elimination, the increase in glucaric acid excretion was significantly higher in the intramuscularly treated neonates. Infants with orally administered phenobarbital showed only insignificantly greater glucaric acid elimination. The decrease of serum bilirubin levels was more pronounced in the intramuscularly treated than in the orally treated group. The determination of glucaric acid may be an important reflection of hepatic microsomal induction of the enzymes of the glucuronic acid pathway.