Effects of formoterol and salmeterol on resting inspiratory capacity in COPD patients with poor FEV1 reversibility

Background: Recent studies suggest that inspiratory capacity (IC) measured at rest can be used to predict improvements in dyspnea and exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. In this study we compared the effect of formoterol (Foradil* Aerolizer*) and salmeterol (Sereventdagger Diskusdagger) in terms of IC in patients with COPD. Methods: This was a multicentre, randomized, placebo-controlled, single-dose, double-dummy, crossover study conducted in five secondary care centres in four European countries. A total of 47 patients with Stage II and III COPD, as defined by ATS criteria, with an increase in forced expiratory volume in 1 s (FEV1) of less than or equal to 12% from the patient's predicted normal value after salbutamol inhalation were included. Patients inhaled single doses of formoterol (12 and 24mug), salmeterol (50 and 100 mug) or matching placebo. IC was recorded before dosing and at 5, 10, 15 and 30 min and 1, 2, 3 and 4 h post-dose. Results: Formoterol was significantly superior to salmeterol during the first hour post-dose as indicated by notable differences at all times during the first hour post-dose and by the ANCOVA analysis of the Area Under the IC Curve (AUC(0-1h)). Conclusions: Both formoterol and salmeterol increase IC in patients with COPD, with formoterol 12mug showing a significantly greater increase in IC over the first hour post-dose than salmeterol 50mug, consistent with a more rapid onset of action.