This paper reveals the effect of carrier particle size to the performance of dry powders for inhalation. Three lactose carriers of different size were investigated using micronized budesonide as drug.  Aerodynamic particle sizing using NGI clearly reveals that the carrier particle size, or more correctly, carrier particle weight, directly influences formulation dispersibility, both for high shear and Turbula blended formulations. In high shear mixing, a large carrier must therefore be mixed at low speed and/or a short time, otherwise the fine particle fraction will rapidly approach zero. A comparison between data generated in two different inhalers (a capsule inhaler and the Novolizer®) revealed that while a stronger device can yield a higher fine particle dose, the relative decline in fine particle fraction is determined solely by the mixing process.

Interestingly, formulations prepared in the Turbula® blender display an opposite trend, i.e. dispersibility was found to increase with increasing mixing energy and thus with carrier particle mass. This points to different mechanisms controlling the performance in the two mixers.

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