Worsening of underlying bronchospasm may be associated with acute exacerbations of chronic obstructive pulmonary disease (COPD). As airway obstruction becomes more severe, the therapeutic option is to add a short-acting inhaled beta2-agonist as needed to cause rapid relief of bronchospasm. Unfortunately however, the most effective dosage may increase above that recommended during acute exacerbations. Formoterol (Oxis) Turbuhaler has a rapid onset of action (within minutes) and demonstrates a maintained effect on a rway function. In this study, we examined the effects of formoterol used as needed in 20 patients with acute exacerbations of COPD. A dose response curve to inhaled formoterol (9 microg per inhalation) or placebo was constructed using three separate inhalations, i.e. a total cumulative dose of 27 microg. Dose increments were given at 20-min intervals, with measurements being made 15 min after each dose. Formoterol, but not placebo, induced a large and significant (P<0.001) dose-dependent increase in forced expiratory volume in 1 sec (FEV1) [mean differences from baseline = 0.1311 after 9 microg formoterol (95% CI: 0.096-0.167)] 0.1811 after 18 microg formoterol (95% CI: 0.140-0.2221) and 0.2081 after 27 microg formoterol (95% CI: 0.153-0.2631). However, 27 microg formoterol did not induce further benefit [0.0271 (95% CI: -0.008-0.0621); P=0.121] when compared wth 18 microg formoterol. Results of this study suggest the use of higher than customary dose of formoterol for as-needed therapy to provide rapid relief of bronchospasm in patients suffering from acute exacerbations of partially reversible COPD.