Comparison of the effects of salmeterol and formoterol on airway tone and responsiveness over 24 hours in bronchial asthma

The recent development of new beta 2-adrenoceptor agonists with a duration of action in excess of 12 h may change strategies in the treatment of bronchial asthma. This study aims at the direct comparison of the main representatives of this new class of drugs, formoterol (F) and salmeterol (S), in asthmatic patients over the course of 24 h. Twelve patients with mild bronchial asthma participated in a double-blind, randomized, placebo-controlled clinical trial. In a dose-finding study we determined the protective and bronchodilating effects of 12 and 24 micrograms F aerosol vs 50 and 100 micrograms S 30 min after inhalation. In a 24-h study we investigated the effects of 12 micrograms F and 50 micrograms S on airway tone and responsiveness. Bronchial responsiveness was assessed as the dose of methacholine necessary to decrease FEV1 by 20%. In the dose-finding study, compared with placebo, all doses of F and S equally increased FEV1 (p < 0.003) and protected against inhaled methacholine (p < 0.0001). In the 24-h study 12 micrograms F and 50 micrograms S increased FEV1 and significantly protected against methacholine-induced bronchoconstriction up to 24 h (p < 0.05), compared with placebo. Phase and amplitude of the circadian variation of FEV1 and airway responsiveness were not affected. Clinically recommended doses of aerosolized F (12 micrograms) and S (50 micrograms) have a duration of action up to 24 h and are equally effective at bronchodilation and protection in acute experiments in patients with mild bronchial asthma.