Ipratropium Bromide: Bronchodilator Action and Effect on Methacholine-Induced Bronchoconstriction

The effects of ipratropium bromide (80 and 200 micrograms) and placebo on the basal bronchial tone and on methacholine-induced bronchoconstriction were investigated in 10 asthmatic patients in a placebo-controlled double-blind manner. Bronchial hyperreactivity to methacholine was confirmed at a pretrial bronchial challenge. The patients were randomly allocated to two groups in which the drug was inhaled from either metered-dose inhalers (MDI) or powder capsules. With the high dosage, the bronchodilation resulting from powder capsules was somewhat more pronounced than that achieved with the MDI. Otherwise the bronchodilator effect of ipratropium bromide and the protection afforded by the drug against methacholine-induced bronchoconstriction were similar in the two groups. In five patients the bronchodilator effect was better and in four patients the tolerance to methacholine was greater after the higher ipratropium dosage than after the lower one. In two patients ipratropium bromide had no bronchodilator effect but gave good protection against methacholine-induced bronchoconstriction. It is concluded that some patients benefit from a dosage of ipratropium bromide higher than that usually recommended and that an anticholinergic effect on the bronchi is possible even in the absence of the bronchodilator effect in the basal state.