Protective effect and duration of action of inhaled formoterol and salbutamol on exercise-induced asthma in children

Abstract

The magnitude and duration of protection against exercise-induced asthma (EIA) afforded by salbutamol and the new, long-acting β 2-agonist, formoterol, were compared in a double-blind, placebo-controlled crossover study. Twelve children with asthma and EIA (>25% fall from baseline at a pretrial exercise test) were studied on 3 different days receiving, in random order, either formoterol, 12 μg, salbutamol, 200 μg, or placebo by inhalation. The effect on EIA was evaluated by standardized treadmill-exercise tests repeated at the following times after medication: 1 2 hour (test 1), 3 hours (test 2), and, if the trial drug still demonstrated an effect, 5 1 2 hours (test 3) and 8 hours (test 4). The mean (SD) maximum percent fall in FEV 1 at the pretrial test was 45% (14%). Placebo treatment had no effect on EIA. The mean (SD) maximum percent fall in FEV 1 was 44% (14%) (test 1) and 39% (13%) (test 2) (not significant). Salbutamol offered good protection against EIA after 1 2 hour (percent fall in FEV 1 18% [18%]; p < 0.02) but was not significantly different from that of placebo after 3 hours, 39% (13%) fall in FEV,. Formoterol blocked EIA in all the children and demonstrated a significant effect in most children for at least 8 hours. The percent fall in FEV, after the various tests were 8% (16%) (test 1), 10% (9%) (test 2), 18% (15%) (test 3), and 18% (7%) (test 4; N = 9) (all tests, p < 0.001). The mean duration of a 50% reduction in EIA was 1 built1 2 hours for salbutamol and 6 1 2 hours for formoterol ( p < 0.001). No side effects were observed. Inhaled formoterol was determined to be more effective and offered four to five times longer protection against EIA than salbutamol.