Effect of tiotropium on mucus hypersecretion and airway clearance in patients with COPD

Increased sputum production is an important feature of COPD, in which a large amount of secretions stagnated in the respiratory lumen may aggravate airflow limitation, impair airway mucociliary transport, and cause recurrent respiratory infection and, hence, acute exacerbations of the diseases. There is evidence that airway mucus hypersecretion is associated with the severity and prognosis of COPD, but the symptoms are generally difficult to treat.

In an open, non-controlled study, we examined the effect of the anticholinergic agent tiotropium on airway mucus hypersecretion in 22 COPD patients. After a 4-week run-in period, the patients received 18 μg of tiotropium once daily delivered through the handihaler for 8 weeks, while symptoms and their impact associated with sputum were scored according to cough and sputum assessment questionnaire (CASA-Q). At week 0 and week 8, spirometry was performed before and 30 min after the administration of albuterol. To test the effect of tiotropium on airway mucociliary transport, nasal clearance time was measured. To evaluate airway mucus production, solid composition of the sputum (dry/wet weight ratio) was measured.

Treatment with tiotropium increased both prebronchodilator FEV1 and postbronchodilator FEV1. Tiotropium decreased cough symptom scores and provided with favorable influences on sputum-related symptoms, and none of the patients complained of worsening of the symptoms judging from the CASA-Q score. Both solid composition of the sputum and mucin contents decreased and nasal clearance time was shortened from 29.4 ± 5.1 to 20.6 ± 4.1min (p < 0.05) during the 8-week treatment.

Tiotropium decreases symptoms associated with sputum in COPD patients, an effect that may be related to the inhibition of airway mucus hypersecretion and improvement of airway mucociliary clearance.