Surface energy considerations in ternary powder blends for inhalation

The need for optimisation of DPI formulations is a main research motivation in respiratory drug delivery. Well-established formulations like carrier-based blends still show a lack of efficiency. The addition of extrinsic fine excipients is extensively discussed since decades, supported by a wide range of solid-state characteristics to understand their mechanism and classify influencing parameters. The first part of this study aims at comparing the surface energies of lactose fines and their corresponding influence on the aerodynamic performance of the respective ternary blends. Five different fine lactose qualities with varying origins were used, which were distinguishable in terms of surface energy, but comparable regarding particle size, moisture content and chemical composition. It demonstrates the crucial influence of adhesion properties of fines, based on different surface energies. Secondly, one specific fine lactose quality was used on fundamentally different lactose carriers, which highlights the negligible influence of carrier properties if extrinsic fines are preferentially capable of excipient-drug interactions.