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 per cent 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 220 mug) 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 per cent fall in the FEV(1). This concentration was the "new" PC(20)FEV(1). Results. F in a dose of 25 mug protected 2 of the 9 children, in a dose of 50 mg protected 4 of the 9 and in doses of 100 and 200 mug 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 mug of F is capable of inducing bronchoprotection in children with mild/moderate asthma.