[Effects of inhaled anticholinergic agents and beta 2-agonists on distilled water induced cough in patients with chronic cough].

The purpose of this study was to evaluate the usefulness of ultrasonically nebulized distilled water (UNDW) inhalation for assessing cough receptor sensitivity and also the effects of inhaled anticholinergic agents and beta 2-agonists on the number of coughs induced by the UNDW inhalation in patients with chronic cough. All patients were non-smokers and had neither bronchial hyperreactivity nor atopic status. We studied the effects of inhaled oxitropium bromide (300 micrograms) and fenoterol hydrobromide (600 micrograms) on the number of coughs induced by UNDW inhalation for 3 minutes in 9 patients with chronic cough and the effects of inhaled fenoterol hydrobromide (400 micrograms) on the number of coughs induced by UNDW inhalation for 1 minute in 8 patients with chronic cough using a randomized, double-blind, cross-over method. There was no significant difference in pulmonary function test results before and after UNDW inhalation. In both the 3-minute and 1-minute UNDW inhalation studies, the number of coughs was greater in the patients than in normal subjects. Patients with chronic cough may have a high level of cough sensitivity, inhaled fenoterol significantly reduced the number of coughs in the patients in both the 3-minute and 1-minute UNDW inhalation studies (p < 0.05). However, compared with control, inhaled oxitropium did not reduce the number of coughs caused by the 3-minute UNDW inhalation in the patients. Tachyphylaxis was observed in normal subjects in the 3-minute UNDW inhalation study when repeated at a 30-minute interval. We conclude that 1-minute UNDW inhalation method may be safe and useful for measuring cough receptor sensitivity of patients with chronic cough and that inhaled beta 2-agonists may have an inhibitory effect on cough induced by irritation of cough receptors through unknown mechanisms other than the bronchodilator effect.