Comparison of the Protective Effect of Formoterol and of Salmeterol against Exercise-Induced Bronchospasm when Given Immediately before a Cycloergometric Test

Abstract

Background: Salmeterol and formoterol, two long-acting β₂-adrenergic agonists, have been shown to be effective against exercise-induced bronchospasm (EIB) several hours after inhalation, but no study has yet compared their protective effect immediately after administration. Objectives: To compare the protective effect of inhaled formoterol and salmeterol against EIB immediately and 4 h after administration. Methods: Double-blind, two-period cross-over study of 11 EIB-positive asthmatic subjects (mean age 21.2 years) administered formoterol 24 µg and salmeterol 50 µg by means of metered-dose inhalers (MDIs) on 2 days separated by an interval of 72 h; the subjects performed two cycloergometric exercise tests immediately and 4 h after dosing. Forced expiratory volume (FEV₁) measurements were made before and at the end of exercise, and then after 3, 5, 10, 15, 20, 25 and 30 min. The maximum percentage decrease in FEV₁ in the 30 min following exercise was considered. Results: Immediately after drug administration, but not 4 h later, formoterol provided significantly better protection against EIB than salmeterol (p = 0.02). The number of formoterol-treated subjects protected against EIB (i.e. with a <15% decrease in FEV₁ after treatment) was 10/11 after the first exercise test and 7/8 after the second; the corresponding figures after salmeterol treatment were 5/11 and 7/8. Conclusions: Our results show that formoterol inhaled via an MDI is effective in preventing EIB as early as within a few minutes of administration, whereas salmeterol does not offer any appreciable protection. On the contrary, the protective effect of the two drugs is clinically equivalent 4 h after administration.