Background: Although long-acting muscarinic receptor antagonists are central to the management of chronic obstructive pulmonary disease (COPD), inhaled medicines may have technical difficulty in some patients and adherence barriers. Methods: A multicenter, randomized, double-blind, placebo-controlled 3×3 crossover Phase II trial was performed to evaluate the efficacy and safety of oral administration of the antimuscarinic agent imidafenacin in patients with COPD. Twenty-seven male COPD patients with % forced expiratory volume in 1 s (FEV1) =30% and <80% predicted were randomized to single oral dose of imidafenacin 0.1 mg, imidafenacin 0.2 mg, or placebo. Results: Maximum change in FEV1 with both doses of imidafenacin significantly improved from baseline to 24 hrs after administration when compared with a placebo. Area under the curve in FEV1 during 24 hrs after administration with 0.2 mg, but not 0.1 mg dose, was significantly improved when compared with a placebo, and the improvement was significantly based on dosedependent manners. Plasma imidafenacin level was positively correlated with change in FEV1. All subjects with both doses of imidafenacin completed without moderate nor severe adverse events. Conclusion: A single oral dose of imidafenacin 0.1 mg or imidafenacin 0.2 mg may contribute to the improvement of pulmonary function with excellent safety and tolerability in patients with COPD. Trial registration: JapicCTI-121760 (Japan Pharmaceutical Information Center - Clinical Trials Information [JapicCTI]; http://www.clinicaltrials.jp/user/cteSearch_e.jsp).
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