Increased theophylline metabolism in premature infants after prenatal betamethasone administration.

The pattern of theophylline metabolites in plasma was studied in 9 preterm neonates of 28-35 weeks gestation. In infants not exposed to corticosteroids prenatally, metabolite formation was dependent on gestational age, postnatal age and/or duration of theophylline therapy. Infants prenatally exposed to betamethasone clearly showed evidence of demethylation and oxidation of theophylline during the first week of life, indicating prenatal activation of the hepatic monooxygenase enzyme system. Preliminary half-life data suggests that activation of hepatic metabolism may not affect initial elimination of theophylline.