Bronchodilator effects of oxitropium bromide, fenoterol, and their combination in normal subjects

Oxitropium bromide is a quaternary anticholinergic compound based on the scopolamine molecule instead of atropine. The purpose of this study was to compare the bronchodilator effects of oxitropium, a beta 2-agonist fenoterol, and their combination, on basal bronchomotor tone in normal subjects. Partial flow-volume curve (PEF25), was measured as an index representing bronchomotor tone. The cumulative dose-response curve of oxitropium bromide inhaled from a metered-dose inhaler was determined in eleven normal subjects. Measurement of PEF25 was repeated every 1 h for 8 h after inhalation of oxitropium (200 micrograms), fenoterol (200 micrograms), their combination or placebo in six normal subjects in a randomized, single-blinded, placebo-controlled, cross-over manner. As the percentage increase in PEF25 by 200 micrograms of oxitropium (45 +/- 6%) was equivalent to nearly 80% of that by dose of 1,600 micrograms (58 +/- 8%), the dose of 200 micrograms is thought to be appropriate. The group mean percentage increase in the PEF25-time course curve was significantly greater after treatment with the combination than with placebo (p < 0.001) and fenoterol (p < 0.001) but not with oxitropium bromide, while the increase in PEF25 following the combination was significantly greater than that following oxitropium bromide after 2 and 3 h. These findings indicate that in normal subjects oxitropium has a powerful bronchodilator effect and that the addition of oxitropium to fenoterol caused greater bronchodilation in normal subjects.