Tiotropium respimat® versus hHndiHaler®: Comparison of bronchodilator efficacy of various doses in clinical trials

Introduction: The long-acting muscarinic antagonist tiotropium bromide is approved in many countries as maintenance therapy for chronic obstructive pulmonary disease (COPD). Tiotropium is available as a dry-powder formulation delivered via HandiHaler (18 lg once daily) and is now also approved as an aqueous solution delivered via the Respimat Soft Mist TM Inhaler (5 lg once daily, 2 puffs of 2.5 lg). Several studies have compared the efficacy of tiotropium HandiHaler (18 lg once daily) with different doses of Respimat. We aimed to compare available bronchodilator efficacy data of once-daily Respimat 1.25, 2.5, 5, 10, 20 lg, and HandiHaler 18 lg to investigate which dose of tiotropium delivered by Respimat is the closest match to tiotropium HandiHaler. Methods: Evaluation of six clinical trials (duration from 3 weeks to 2-3 years) that included lung function measures (trough forced expiratory volume in 1 s and trough forced vital capacity) as key outcomes. Results: In the six trials, bronchodilator efficacy of Respimat 5 lg and HandiHaler 18 lg was similar; however, reduced bronchodilator efficacy was observed with lower doses of Respimat (1.25 and 2.5 lg). Conclusion: These findings support the use of the marketed once-daily dose of Respimat 5 lg for the maintenance treatment of patients with COPD. Funding: Boehringer Ingelheim.