Background: In contrast to the well-known activity profile in asthma, the precise efficacy and optimum dose schedules of long-acting beta(2)-agonists in chronic obstructive pulmonary disease (COPD) are not clear.
Objective: In this study, we aimed to compare the onset and the duration of action of a single inhalation of formoterol and salmeterol in COPD patients having partially reversible airway obstruction.
Methods: In a double-blind, randomized, crossover and placebo-controlled study design, the respiratory functions of 22 patients (mean age 57.3+/-5.4 years) having mild to severe COPD (5 mild, 8 moderate and 9 severe) and partially reversible airway obstruction [mean baseline reversibility of forced expiratory volume in 1 s (FEV(1)) 19.3+/-3.1%] were evaluated after inhalation of 12 microg formoterol and 50 microg salmeterol.
Results: Regarding the onset of bronchodilator action, the mean absolute increase of 0.20 liters in FEV(1) 10 min after inhalation of formoterol was significantly higher than baseline and that of placebo (0.04 liters), whereas that of salmeterol (0.11 liters) did not reach statistical significance. At 20 min, both formoterol (0.25 liters) and salmeterol (0.20 liters) produced a significant increase in FEV(1) compared with baseline and with that of placebo (0.04 liters). The peak bronchodilator effects occurring at 60 and 120 min following formoterol (0.39 liters) and salmeterol (0.40 liters) inhalation, respectively, were significantly higher than the corresponding levels of placebo (0.02 and -0.12 liters, respectively). Concerning the duration of action, the 12-hour values of both formoterol (0.25 liters) and salmeterol (0.22 liters) were significantly higher than that of placebo (-0.12 liters). The area under the curve values of FEV(1) of formoterol (3.5+/-1.3 l.h) and salmeterol (3.2+/-1.2 l x h) averaged over 12 h were comparable and higher than placebo values (1.2+/-0.5 l x h). After formoterol inhalation 2 patients experienced tremor and 1 had palpitation; 1 tremor and 1 headache attack were noted after salmeterol. For the pharmacologically predictable side effects, there was no difference between the drugs.
Conclusions: In conclusion, this study revealed that a single dose of 12 microg formoterol and 50 microg salmeterol provided comparable bronchodilation within 12 h and had tolerable side effects in patients with mild to severe COPD having partially reversible airway obstruction.