Comparison of the protective effect of formoterol and of salmeterol against exercise-induced bronchospasm when given immediately before a cycloergometric test.

BACKGROUND

Salmeterol and formoterol, two long-acting beta(2)-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 microg and salmeterol 50 microg 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 (FEV(1)) 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 FEV(1) 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 FEV(1) 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.