Dose-response study of oxitropium bromide inhaled as a nebulised solution

Twelve patients suffering from partially reversible chronic obstructive pulmonary disease (COPD) took past in a single blind, randomised, 4-way cross-over trial to determine the optimal dose and duration of action of the anticholinergic agent oxitropium bromide (OTB) inhaled as a nebulised solution. Single doses of 500, 1000, 1500 and 2000 micrograms nebulised OTB were compared during a 6 hour-observation period. Lung function test results indicated that 500 and 1000 micrograms OTB only induced slight bronchodilatation, whereas 1500 and 2000 micrograms OTB produced a significantly greater increase in mean FEV1 compared to 500 micrograms. There was a trend for 2000 micrograms to be superior to 1000 micrograms, but 2000 micrograms and 1500 micrograms were not significantly different. Significant bronchodilatation (> 15% rise in FEV1 from baseline) persisted for 6 h after 1500 micrograms. A significant decrease in airway resistance (Raw) was observed following inhalation of 2000 micrograms. The mean decrease in Raw was 33% after 30 min, 20% after 4 h and 12% after 6 h. In this trial, 2000 micrograms OTB administered by an ultrasonic nebuliser was the optimal dose, but a satisfactory result was also obtained with 1500 micrograms.