Effect of erythromycin on theophylline clearance in asthmatic children

Fifteen asthmatic children (mean age = 14.5 years) who required daily theophylline therapy were studied for effect of erythromycin ethyl-succinate on theophylline clearance. After a one week course of EES, there was 25.8 +/- 18.4% reduction in theophylline clearance rate (P less than 0.001), and a concomitant elevation in steady-state serum theophylline concentration of 40.0 +/- 35.3% (P less than 0.01). Three subjects reached serum theophylline concentrations greater than 20 micrograms/ml. Patients receiving therapeutic doses of theophylline are at considerable risk of theophylline toxicity if EES is co-administered.