Efficacy and duration of action of placebo responses in the prevention of exercise-induced asthma in children

Exercise-induced bronchoconstriction, a common phenomenon in asthmatic children, may be prevented by the administration of appropriate drugs. In this study we evaluated the effect and duration of action of placebo (Freon gasses) administered to the patients as a protective drug. The maximum decrease in forced expiratory volume in 1 second (FEV1) after exercise testing was 40.3% +/- 3.10 at the initial screening session and, on different study days, 23.3% +/- 3.57, 28.8% +/- 3.86, and 33.7% +/- 3.71 30, 120, and 240 minutes, respectively, after the administration of Freon gasses. There was a linear trend indicating a reduction in protection with time. The placebo effect was marked 30-120 minutes after treatment (p less than 0.01) and completely disappeared after 4 hours. The placebo effect should always be considered in the evaluation of any new antiasthmatic drug