Hydroxypropyl Methylcellulose Capsules Enhance Aerodynamic Performance of Carrier-Based Dry Powder Inhaler...

Background/Objectives: This study aims to investigate the underexplored impact of capsule type on the performances of capsule-based dry powder inhalers (cDPIs). It compares specific properties of hard gelatin-based capsules (Hard Gelatin Capsules (HGC), HGC including polyethylene glycol (HGC + PEG)) and hypromellose-based capsules, (Zephyr^® Vcaps^® (VC), Zephyr^® Vcaps^® Plus (VCP) and Vcaps^® Plus Zephyr Inhance™ (VCP-I)) with aerosolization performances of model carrier-based formulation, providing insights into their impact on pulmonary drug delivery efficacy. Methods: Aerosolization properties of a model phenytoin/lactose blend formulation filled in the different capsules was evaluated using a Next Generation Impactor (NGI) with RS01 device. Capsule shell characteristics were evaluated in terms of water activity, static charges, and inner surface aspect and roughness. Results: Hypromellose-based capsules, especially VC and VCP-I, exhibited significantly higher drug delivery performances compared to gelatin-based capsules. In particular, VCP-I demonstrated good results with excellent batch-to-batch reproducibility and 51% of the nominal dose available for lung absorption. Although capsule inner surface showed clear differences between both polymer families, no clear correlation could be found between cDPI performances and capsule roughness and density of charge. All capsules presented good mechanical properties in the conditions of the tests. Conclusions: Capsule type exerts a significant impact on cDPI performances. These findings highlight the importance of capsule selection as a critical material attribute in the design and optimization of inhalation products.