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Inhalation OctOber 2018 21 two blender types produced comparable results with the selected parameters. Consequently, a production of ordered mixtures based on Parteck M DPI with both methods is equally possible. Storage stability Given that previous experiments did not show any dif- ference between the two preparation methods, blends for storage stability assessment were prepared with the Turbula blender. Again, both blends reached suitable homogeneity, comparable to the first set of blends (RSD < 1.45% and recovery > 97.06%). For the BUD blend, there was no significant difference in FPF over storage time, irrespective of storage condi- tions (Figure 7). It was observed that the FPF decreased after two months at 75% RH but this effect was not sig- nificant due to a higher standard deviation. is shows that for BUD as a model substance for hydrophobic APIs, the high physical stability of the mannitol carrier can be a decisive factor in providing constant FPF val- ues over a long storage period. In the SBS blend, the effect of storage at increased humidity was more pronounced because a hydrophilic carrier was blended with a hydrophilic API. Price, et al. 14 were able to demonstrate that interparticulate forces were more dominant between SBS and a hydro- the Picomix mixer) could lead to higher press-on forces and therefore to a lower inhalable fraction. In contrast, shear forces are needed to overcome API cohesion and distribute individual API particles on the carrier sur- face. e impact of these two theories seems to be bal- anced here because none of the influencing factors was predominant in the results. Similarly, the BUD blends did not exhibit significant differences using the Cyclohaler (p FPF > 0.440; p FPD > 0.146), but it should be noted that the FPF and FPD of the mixture from the Picomix tested with the Novolizer was 16% or 28 μg higher than from the Tur- bula blender. e delivered dose between these BUD blends did not show a significant difference (p = 0.925). A reason for the difference in FPF and FPD could be the changes in particle size, as shown in Figure 5. e parti- cle size distribution exhibited a greater amount of larger particles due to the already-described decrease of fine particles (< 15 μm). In the Novolizer, the main disper- sion principle is inertial forces, which are very strong and thereby able to disperse the adhesive mixture, even if particles adhere quite intensely to the carrier. 12 Larger particles have a higher inertia and therefore increase the inhalable fraction. at this effect was not observed for the SBS blends was possibly due to the higher adhesion forces between SBS and mannitol. 13 In summary, the Figure 6 Fine particle fraction (FPF) (%), fine particle dose (FPD) (μg) and delivered dose (μg) from all four blends (BUD = gray, SBS = blue) tested with the Novolizer (N) and with the Cyclohaler (C); mean values with standard deviation; n = 3 50 40 30 20 10 0 50 40 30 20 10 0 100 80 60 40 20 0 200 150 100 50 0 Fine particle fraction (%) Fine particle fraction (%) Fine particle dose (μg) Fine particle dose (μg) Delivered dose (μg) Delivered dose (μg) 100 80 60 40 20 0 200 150 100 50 0 Turbula - N Turbula - N Turbula - N Turbula - N Turbula - N Turbula - N Picomix - N Picomix - N Picomix - N Picomix - N Picomix - N Picomix - N Turbula - C Turbula - C Turbula - C Turbula - C Turbula - C Turbula - C Picomix - C Picomix - C Picomix - C Picomix - C Picomix - C Picomix - C