The protective effects of ipratropium bromide and terbutaline on distilled water-induced bronchoconstriction.

In a randomized, double-blind, placebo-controlled study, we investigated the protective effects of ipratropium bromide 160 micrograms and 320 micrograms and terbutaline 500 micrograms on ultrasonically nebulized distilled water (UNDW)-induced bronchoconstriction in nine stable asthmatic patients. Both drugs caused a significant increase (P < 0.001) in baseline FEV1 with no significant differences between the drugs or both doses of ipratropium bromide. Pre-inhalation of ipratropium bromide 320 micrograms and terbutaline 500 micrograms inhibited UNDW-induced bronchoconstriction (P < 0.01), whereas ipratropium bromide 160 micrograms had no protective effect. The protective effects of ipratropium bromide showed a large interindividual variation. There was no correlation between the increase in baseline FEV1 and PD20 UNDW, indicating that the protective effect on UNDW-induced bronchoconstriction is not dependent on the bronchodilation induced by terbutaline and ipratropium bromide. It also appears that the UNDW-induced bronchoconstriction is at least partly vagally mediated.