Since it has frequently been observed that high serum levels of theophylline are difficult to control in children,we monitored serum theophylline concentrations in 868 patients,of which 322 received the drug as a continuous infusion.Generally,serum theophylline concentrations vary greatly among individuals and this is considered to be due to differences in clearance.
In this study,we investigated the relationship between age and serum theophylline concentration and theophylline clearance,finding that there was a weak association between dosage and serum concentration in all the age groups,which was not meaningful.Our results also suggested that theophylline clearance in children was greater than that in adolescents and adults,with the clearance in children in the 1-5 years (preschool) and 6-8 years age ranges being higher than that for patients in the 9-12 and 13-53 years age ranges.Our results suggested that the dosage should be determined based on theophylline clearance calculated with respect to age instead of on the standard value of 0.04 (L/kg/hr) given in textbooks.