The principle of carrier-based blends is well established in formulations for dry powder inhalation, as it overcomes problems of micronized drug particles often being cohesive and poorly flowable and hence, creating difficulties in powder handling and dosing.1 In carrier-based blends, micronized drug is adhered on the surface of the carrier and thus, is moved and dosed as if it were a larger particle. For nasal administration, particles larger than 10 μm, probably

better than 50 μm, are required to ensure preferential nasal deposition. Thus, larger particles of carrier-based blends would also be beneficial for deposition. For oral inhalation to the lung, an aerodynamic particle size below 5 μm is needed, hence micronized drug particles in a carrier based blend must be detached from the carrier upon inhalation. Though not completely understood, the detachment of active pharmaceutical ingredient (API) from carrier particles

takes place by dispersion forces that occur during inhalation.