Theophylline pharmacokinetics in the young infant.

The pharmacokinetics of theophylline were investigated in 13 infants, 4 to 18 months of age. An inverse relationship was found between theophylline half-life and age. Volume of distribution did not differ from that reported by other authors in similarly aged infants. Our data suggest that childhood clearance rates of elimination can be achieved by 6 months of age. The decreased theophylline elimination observed in the smaller infant indicates that the usual pediatric dosing recommendations cannot be used routinely. Until more specific data are available in the infant under 6 months, the authors reaffirm individualization of theophylline dosage to maintain therapeutic levels and avoid toxicity.