Salmeterol versus formoterol in patients with moderately severe asthma: onset and duration of action

We evaluated the profile of the bronchodilatory effect of three inhaled beta2-agonists, 24 microg formoterol, 50 microg salmeterol and 200 microg salbutamol, in patients with stable, moderately severe asthma. Thirty asthmatics (mean+/-SD age 54+/-8 yrs; forced expiratory volume in one second (FEV1) 58+/-12% predicted; reversibility of FEV1 21+/-8% from baseline) participated in a single-centre, double-blind, randomized, single-dose, cross-over study. FEV1 was obtained in baseline condition and 10, 20, 30, 60 min, and every hour up to 12 h after inhalation of the trial drug. Specific airway conductance (sGaw) was measured at baseline condition and 1, 3, 5, 7, 10, 20, 30, 60 min, and every hour up to 12 h after inhalation. Formoterol produced a mean increase in sGaw (as % of baseline) of 44% after 1 min, maximal (135%) after 2 h, and 56% after 12 h. The mean increase in FEV1 was maximal (27%) after 2h, and 10% after 12 h. After salmeterol, mean increase in sGaw amounted to 16% after 3 min, maximal (111%) after 2-4 h, and 58% after 12 h. The mean increase in FEV1 was maximally 25% after 3h, being 11% after 12 h. After salbutamol, mean increase in sGaw was 44% after 1 min and maximal (100%) after 30 min. The peak increase in FEV1 was 25%. We conclude that formoterol (24 microg) and salmeterol (50 microg) had an equal bronchodilatory capacity, which was similar to that of 200 microg salbutamol and lasted for at least 12 h in patients with asthma. However, formoterol had a more rapid onset of action than salmeterol, equal to that of salbutamol.