N-acetylcysteine by metered dose inhaler in the treatment of chronic bronchitis: a multi-centre study.

Sixty-five patients with chronic bronchitis were studied at five different centres in a double-blind, randomized trial. Two parallel groups were treated with either N-acetylcysteine or placebo by metered dose inhalers for 16 weeks. Following a 1-week run-in period, each patient recorded subjective impressions of the drug action on their bronchitic symptoms in a diary once a week. In addition, exacerbations were registered. Lung function testing and adverse effects were evaluated by four visits to the chest clinics during the 16 weeks. We could not demonstrate that N-acetylcysteine by metered dose inhalers had any significant effect on patients' feeling of well-being, sensation of dyspnoea, intensity of coughing, mucus production, or expectoration or lung function. Its effect in reducing exacerbations could not be estimated because of a very low number of exacerbations reported. N-acetylcysteine inhalation was safe when used over a 16-week period.