Pharmacokinetics of theophylline in acute asthma

Serum theophylline concentrations were measured in 17 children and adolescents with acute asthma who received an aminophylline loading dose of 7 mg/kg and a constant infusion of 15 mg/kg/24 hours. The mean total theophylline clearance rate was 1.32 +/- S.D. 0.66 ml/min/kg. Hypoxia, and in two patients, acidosis, did not appear to significantly influence theophylline clearance rates. Inter-individual differences in clearance rates were great. No child experienced symptoms or signs of theophylline toxicity during the study. If serum theophylline concentrations cannot be monitored readily, an aminophylline infusion rate of 15 mg/kg/24 hours can be used safely in patients with acute asthma, but in most patients this infusion rate will not provide serum theophylline concentrations in the desired therapeutic range of 10-20 microgram/ml. Monitoring of serum theophylline concentrations during aminophylline infusion is desirable in order to individualize infusion rates, and achieve optimal bronchodilation without toxicity.