Capsule-based, single-dose dry powder inhalers (DPIs) are commonly-used devices to deliver medications to the lungs. This work evaluates the effect of the drug/excipient adhesive bonding and the DPI resistances on the aerosol performance using a combination of empirical multi-stage impactor data and a fully-coupled computational fluid dynamics (CFD) and discrete element method (DEM) model. Model-predicted quantities show that the primary modes of powder dispersion are a function of the device resistance. Lowering the device resistance increases its capacity to transport a wider range of particle size classes toward the outlet and generate more intense turbulence upstream therein. On the other hand, a higher device resistance increases the velocity of the tangential airflow along the device walls, which in turn increases the intensity of particle/device impaction. Correlating model data and experimental results shows that these differing powder dispersion mechanisms affect different formulations differently, with finer aerosols tending to result when pairing a lower resistance device with formulations that exhibit low API/excipient adhesion, or when pairing a high resistance device with more cohesive formulations.
Keywords: CFD-DEM; Computational fluid dynamics; Discrete element method; Dry powder inhalers; Inhalation drug delivery.
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