Comparative in vitro assessment of dual and triple combination inhalers using an integrated aerosol–epithelial model

Dual and triple combination pressurised metered-dose inhalers are widely used for the management of obstructive airway diseases; however, the influence of triple therapy on aerosol–epithelium interactions remain incompletely characterised. This study investigated whether the tested triple combination formulation differs from the dual therapy inhaler in terms of drug dissolution, transepithelial permeation, and barrier responses compared with a dual therapy inhaler. An integrated in vitro platform combining a modified Next Generation Impactor with H441 air–liquid interface cell layers were employed to enable size-resolved aerosol deposition followed by assessment of dissolution, transepithelial permeation, barrier integrity, and cytotoxicity. Drug quantification was performed using LC–MS. Dissolution profiles of beclometasone, formoterol, and glycopyrronium were comparable between formulations across deposition stages. In contrast, the triple combination inhaler demonstrated higher early transepithelial permeation of beclometasone, and formoterol compared with the dual formulation, while glycopyrronium transepithelial permeation was stage independent. Exposure to the triple formulation increased transepithelial electrical resistance without altering paracellular permeability. Both inhalers maintained high cell viability under deposition conditions, with cytotoxicity observed only for formoterol at supratherapeutic concentrations. These findings indicate that the tested triple and dual formulations exhibit differences in early transepithelial permeation kinetics and barrier responses following aerosol deposition, without corresponding differences in dissolution behaviour, highlighting the utility of integrated aerosol–cell models for mechanistic evaluation of inhaled combination formulations.