Influence of higher than conventional doses of oxitropium bromide on formoterol-induced bronchodilation in COPD

We examined the influence of higher than conventional doses of oxitropium bromide on formoterol-induced bronchodilation in patients with partially reversible stable COPD. Twenty outpatients inhaled one or two puffs of formoterol (12 mu g puff(-1)), or placebo. Two hours after inhalation, a dose-response curve to inhaled oxitropium bromide (100 mu g puff(-1)) or placebo was constructed using one puff, one puff, two puffs and two puffs, for a total cumulative dose of 600 mu g oxitropium bromide. Doses were given at 20-min intervals and measurements made 15 min after each dose. On six separate days, all patients received one of the following: (1) formoterol 12 mu g + oxitropium bromide 600 mu g, (2) formoterol 12 mu g + placebo, (3) formoterol 24 mu g + oxitropium bromide 600 mu g, (4) formoterol 24 mu g + placebo, (5) placebo + oxitropium bromide 600 mu g; or (6) placebo + placebo. Both formoterol 12 mu g and 24 mu g induced a good bronchodilation (formoterol 12 mu g, 0.19-0.20 1; formoterol 24 mu g 0.22-0.24 1). The dose-response curve of oxitropium, but not placebo, showed an evident increase in FEV1, with a further significant increase of respectively 0.087 1 and 0.082 1 after the formoterol 12 mu g and formoterol 24 mu g pre-treatment. This study shows that improved pulmonary function in patients with stable COPD may be achieved by adding oxitropium 400-600 mu g to formoterol. There is not much difference in bronchodilation between combining oxitropium with formoterol 12 mu g or 24 mu g In any case, formoterol 24 mu g alone seems sufficient to achieve the same bronchodilation induced by oxitropium 600 mu g alone in most patients. (C) 1999 HARCOURT PUBLISHERS LTD.