Effects of the addition of tiotropium on airway dimensions in symptomatic asthma

Background: Tiotropium, a once-daily, long-acting anticholinergic bronchodilator, has shown efficacy and safety as an add-on to maintenance therapy in patients with symptomatic asthma. Objective: The aim of the present study was to assess the effect of tiotropium on airway geometry and airway inflammation in patients with asthma who were symptomatic despite treatment with inhaled corticosteroid (ICS) plus a long-acting beta 2-agonist (LABA). Methods: In total, 53 patients with symptomatic asthma who received ICS plus LABA and who had a prebronchodilator forced expiratory volume in 1 second of 60-90% of the predicted value were randomized to the addition of tiotropium 5 mu g once daily (n = 25) or no add-on (n = 28) to maintenance therapy for 48 weeks. Quantitative computed tomography, fractional exhaled nitric oxide, and pulmonary function were measured. Results: Compared with maintenance therapy, the addition of tiotropium significantly decreased airway wall area (WA) corrected for body surface area (BSA) (WA/BSA) (p < 0.05) and wall thickness (T) (T/root BSA, p < 0.05), and improved airflow obstruction. No significant difference in the change of fractional exhaled nitric oxide was observed between the two treatment groups. Changes in WA/BSA and T/root BSA were significantly correlated with the change in predicted forced expiratory volume in 1 second (r = -0.87, p < 0.001, and r = -0.82, p < 0.001, respectively). Conclusion: The addition of once-daily tiotropium to maintenance therapy improved airflow limitation and reduced airway T. A triple combination of tiotropium and ICS plus LABA may have additive protective effects of bronchodilation and remodeling.