Methacholine challenge in the evaluation of chronic cough.

Inhalation challenge with methacholine is helpful in establishing the diagnosis of hyperreactive airways disease and its association with cough. It remains a valuable, safe, diagnostic tool. It appears that cough resulting from hyperreactive airways disease is a common clinical disorder that can be treated successfully in nearly all patients. Fifty percent of these patients go on to have more typical signs and symptoms of bronchial asthma over time.