Theophylline metabolism in preterm neonates during the first weeks of life.

The effects of prenatal steroids on theophylline metabolism in infants of 27-32 weeks gestation was studied. Although in utero exposure to betamethasone was associated with a more mature theophylline metabolite pattern in the first days of life, initial elimination half-life (t1/2 beta) did not differ significantly between groups. By the second or third week of life the metabolite pattern was similar in all infants. The decline in t1/2 beta seen during theophylline treatment was not directly related to increased metabolite formation. These data suggest that other factors, such as renal clearance, are more important in determining the pharmacokinetics of theophylline in neonates than is hepatic metabolism.