Should the choice of a long-acting bronchodilator in the long-term therapy of chronic obstructive pulmonary disease depend entirely on the onset of action?

moterol administered via the Aerolizer is well tolerated and results in a higher degree of bronchodilation within the fi rst 2 h and comparable bronchodilation over a period of 12 h compared with tiotropium regarding improvement in FEV 1 . These differences were maintained during a 7-day treatment and might have implications for future treatment of COPD with long-acting bronchodilators. The fact that formoterol elicited a signifi cantly faster onset of action was not an unexpected fi nding. In fact, our study [7] provided strong evidence in favor of this pharmacodynamic behavior, although van Noord et al. [8] have reported that following inhalation of the morning dose of tiotropium or formoterol, the improvements in FEV 1 were comparable between the two bronchodilators until 8 h after dosing. The question of whether FEV 1 really describes the impact of bronchodilators in COPD remains to be determined. It must be borne in mind that in stable COPD patients, a high prevalence of expiratory fl ow limitation exists (about 48%), even when the severity of airway obstruction in terms of FEV 1 is taken into account [9] . FEV 1 – the gold standard for assessing bronchodilator responsiveness – is only weakly correlated with patientcentered outcomes such as dyspnea [10] . In patients with COPD and expiratory fl ow limitation at rest, changes in inspiratory and forced vital capacities after bronchodilator use may represent an objective tool for prescribing Both the Global Initiative for Chronic Obstructive Lung Disease guidelines [1] and the American Thoracic Society/European Respiratory Society position paper [2] recommend regular treatment with long-acting bronchodilators, including tiotropium, rather than short-acting bronchodilators, for moderate/very severe chronic obstructive pulmonary disease (COPD). These recommendations do not differentiate between long-acting 2 -agonists, e.g. salmeterol and formoterol, and tiotropium, although 2 -agonists and anticholinergics are distinct classes of drugs with different mechanisms of action [3] . This is the likely reason for Tennat et al. [4] to suggest that individual COPD patients may respond better to either tiotropium or salmeterol and that an acute bronchodilator test might help to choose the appropriate therapy. However, our group has documented that the bronchodilator effects of tiotropium and salmeterol, evaluated as mean changes from baseline forced expiratory volume in 1 s (FEV 1 ), are similar in patients with stable COPD during the fi rst 3 h after their acute administration, and consequently the choice of prescribing a long-term therapy with a long-acting bronchodilator should not depend on the simple test of reversibility [5] . In the current issue of Respiration , the results of an open, randomized, crossover, clinical trial comparing formoterol and tiotropium in patients with moderate-severe COPD are presented [6] . The authors concluded that for-