Comparison of the protective effect and duration of action of orally administered clenbuterol and salbutamol on exercise-induced asthma in children.

Clenbuterol (C), a long-acting beta 2-selective bronchodilator was compared with salbutamol (S) in exercise-induced asthma (EIA) at two premedication time levels. Sixteen asthmatic children with EIA living at an altitude of 1,750 m were treated with C (0.001 mg/kg) and S (0.12 mg/kg), administered randomly in a double-blind cross-over study 90 and 300 minutes before exercise tests of running on a treadmill for 6 minutes. Pulmonary functions were evaluated prior to the administration of the drugs and immediately before, at the end of, and 2, 5, 10, 15, 20, and 25 minutes after exercise tests. In the preliminary screening exercise test the mean fall of FEV1 was 41.1%, but it was 21.0% and 27.1% after S and 21.9% and 19.9% after C administered 90 and 300 min prior to the test, respectively. Salbutamol administered 300 minutes before the test was statistically less effective than the same drug administered 90 minutes before the test or C administered 300 minutes before the test. Therefore, we can conclude that clenbuterol provides a more lasting protection than salbutamol in EIA.