The effect of angiotensin converting enzyme inhibitors (ACE-I) and selective beta 1-antagonists on bronchial reactivity and the cough reflex in man.

The non-specific bronchial reactivity and cough threshold of hypertensive patients on an ACE-I monotherapy regimen (either captopril or enalapril), a beta 1-antagonist monotherapy regimen (either atenolol or metoprolol) or a combination of an ACE-I with a beta 1-antagonist were determined in the present study. Forty-six hypertensives who were on these medications performed a histamine inhalation test (to assess bronchial reactivity) and a further 36 of these individuals participated in the citric acid test (to assess cough threshold). A control cohort consisting of 25 age-matched, drug-free subjects also performed the citric acid test. The incidence of bronchial hyperreactivity was not significantly different between the ACE-I monotherapy regimen and the beta 1-antagonist monotherapy regimen (Chi-squared = 0.248). However, when the monotherapy regimens were pooled and compared with the ACE-I and beta 1-antagonist combination regimen, the combination regimen was found to be associated with a significantly higher incidence of bronchial hyperreactivity (Chi-squared = 6.69). No difference was observed between the age-matched controls and the hypertensive patients in terms of their cough threshold.