Pharmacodynamics and Pharmacokinetics Following Once-Daily and Twice-Daily Dosing of Tiotropium Respimat(®) in Asthma Using Standardized Sample-Contamination Avoidance

Background: This study was conducted to confirm the 24-hour bronchodilator efficacy and pharmacokinetic profile of once-daily tiotropium Respimat(®) 5 μg add-on to inhaled corticosteroids (ICS) in adults with symptomatic asthma. It used a trial protocol designed to minimize the risk of pharmacokinetic sample contamination resulting from improper sampling procedure, sample handling, or device handling during priming and subsequent inhalation procedure. Methods: A Phase II, randomized, double-blind, two-way crossover study (NCT01696071) comparing two daily dosing regimens of tiotropium for 4 weeks, once-daily 5 μg (evening dosing) or twice-daily 2.5 μg (morning and evening dosing), as add-on to maintenance therapy with ICS (400–800 μg budesonide or equivalent) as controller medication. There was no washout between treatment periods. Results: An increase in the area under the curve of the 24-hour forced expiratory volume in 1 second profile from study baseline was observed following once-daily tiotropium 5 μg (217 mL) and twice-daily 2.5 μg (219 mL), with no difference between the two regimens (−2 mL [95% confidence interval: −38, 34]). In a subset of the study population, total tiotropium exposure, expressed as area under the plasma concentration versus time curve over 24 hours, was comparable between dosing regimens. Unexpected tiotropium plasma levels were observed in two patients, possibly because of contamination. Conclusions: The observed bronchodilator efficacy over 24 hours was similar with once-daily tiotropium 5 μg and twice-daily 2.5 μg as add-on to ICS therapy, supporting the suitability of once-daily dosing to provide sustained improvements in lung function in adults with symptomatic asthma.