Protective effects of different doses of inhaled fenoterol on methacholine-induced bronchoconstriction in asthmatic children

Abstract

Objective: To evaluate the protective effect of different doses of inhaled fenoterol (F) on bronchoconstriction induced by methacholine (M). Design: randomized double-blind study. Setting: Referrence center. Participants: 9 children (aged from 7 to 15 years old), with mild or moderate asthma and allergic to D. pteronyssinus. Intervention: On the first day, the M concentration necessary to induce a 20% fall in the forced expiratory volume in the first second (FEV 1 ; PC 20 FEV 1 ) was determined using closed circuit inhalation (De Vilbiss 646). On subsequent days, the children inhaled a dose of F (25 or 50 or 100 or 200 mg) through the same circuit and, after 15 minutes the FEV 1 was measured, becoming the basal value. Bronchoprovocation was then initiated using the concentration prior to the PC 20 FEV 1 of the first day and continuing until there was a 20% fall in the FEV 1 . This concentration was the "new" PC 20 FEV 1 . Results: F in a dose of 25 mg protected 2 of the 9 children, in a dose of 50 mg protected 4 of the 9 and in doses of 100 and 200 mg protected all children. We did not observe any relationship between the magnitude of the bronchodilation and bronchoprotection induced by the inhalation of F. Conclusions: Our results suggest that a dose of 100 mg of F is capable of inducing bronchoprotection in children with mild/moderate asthma. Uniterms: Asthma. Children. Bronchial hyperreactivity. Beta agonists. Fenoterol. Methacholine.