Pharmacokinetics and Pharmacodynamics of Tiotropium Solution and Tiotropium Powder in Chronic Obstructive Pulmonary Disease

The aim of the study was to characterize pharmacokinetics of tiotropium solution 5 μg compared to powder 18 μg and assess dose-dependency of tiotropium solution pharmacodynamics in comparison to placebo. In total 154 patients with chronic obstructive pulmonary disease (COPD) were included in this multicenter, randomized, double-blind within-solution (1.25, 2.5, 5 μg, and placebo), and open-label powder 18 μg, crossover study, including 4-week treatment periods. Primary end points were peak plasma concentration (C max,ss), and area under the plasma concentration-time profile (AUC0-6h,ss), both at steady state. The pharmacodynamic response was assessed by serial spirometry (forced expiratory volume in 1 second/forced vital capacity). Safety was evaluated as adverse events and by electrocardiogram/ Holter. Tiotropium was rapidly absorbed with a median tmax,ss of 5-7 minutes postdosing for both devices. The gMean ratio of solution 5 μg over powder 18 μg was 81% (90% confidence interval, 73-89%) for Cmax,ss and 76% (70-82%) for AUC0-6h,ss, indicating that bioequivalence was not established. Dose ordering for bronchodilation was observed. Powder 18 μg and solution 5 μg were most effective, providing comparable bronchodilation. All treatments were well tolerated with no apparent relation to dose or device. Comparable bronchodilator efficacy to powder18 μg at lower systemic exposure supports tiotropium solution 5 μg for maintenance treatment of COPD. © 2013 The Authors. The Journal of Clinical Pharmacology Published by Wiley Periodicals, Inc. on behalf of The American College of Clinical Pharmacology.