Pharmacokinetic Bioequivalence of Two Inhaled Tiotropium Bromide Formulations in Healthy Volunteers

BACKGROUND AND OBJECTIVE A novel tiotropium bromide monodose capsule dry powder inhaler (DPI) formulation and device have been developed. The formulation was based on a spray-dried matrix that enhances the aerosolizaton properties, allowing a less active tiotropium metered dose (13 µg/capsule) while maintaining the same delivered dose (10 µg/actuation). This study describes the pharmacokinetic bioequivalence to the reference product. METHODS This randomized, two-stage, crossover, semi-replicate (three-way) study was performed in healthy volunteers. In each study period, subjects received a single dose of two capsules (20 μg delivered dose) of the study medication, separated by a 14-day washout period: tiotropium 10 μg delivered dose (Laboratorios Liconsa, Spain) and Spiriva HandiHaler(®) (Boehringer Ingelheim Pharma GmbH & Co KG, Germany). Blood samples were obtained up to 48 h post-dose to evaluate the comparative bioavailability. Tiotropium was measured in plasma by means of dual stage liquid-liquid extraction followed by the two-dimensional ultra-high performance liquid chromatography sensitive sub-pg/mL bioanalytical method. The main pharmacokinetic parameters were maximum plasma concentration (C max), area under the concentration-time curve (AUC) from time zero hours to the last observed concentration at time t (AUC t ), and AUC from time zero hours to 30 min (AUC0.5). Bioequivalence was accepted if the 90.20 % confidence interval (CI) for the ratio test/reference of the primary pharmacokinetic parameters lay within the acceptance range of 80-125 %. Safety assessment was a secondary endpoint. RESULTS A total of 30 subjects were randomized and bioequivalence was demonstrated for all primary pharmacokinetic parameters: C max (CI 87.26-106.60 %), AUC t (CI 101.33-111.64 %), and AUC0.5 (CI 97.95-113.49 %). Both study treatments were well tolerated (four non-serious adverse events [AEs] were reported in four subjects: one AE before any product administration, two AEs after test product administration; and one AE after reference product administration). CONCLUSIONS Both products containing tiotropium 10 µg delivered-dose DPI were bioequivalent and showed good tolerability and a similar safety profile.