Methacholine inhalation challenge in patients with chronic cough induced by angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme inhibitors (ACEI) cause cough in some patients, but the mechanism of this side effect is not clear. Five patients (group I) who had developed chronic cough induced by ACEI were evaluated to determine the bronchial hyperreactivity (BHR) by challenge with methacholine inhalation using a reservoir method at Respiratory Unit, Chulalongkorn Hospital University. Five patients (group II) who did not experience coughing associated with ACEI were also challenged as controls. The results revealed that two patients (40%) in group I demonstrated BHR with the mean PC20 at 15 mg/ml of methacholine solution. On the other hand, none of the patients in group II disclosed BHR. We concluded that coughing during ACEI therapy may be due to an increased inflammatory state in the airway in some susceptible subjects.