The effect of lactose carrier properties on the fine particle dose from dry powder inhalers in dependence of the inhaler design

Background: Various lactose carrier particle properties arerecognised as being relevant to the fine particle dose (FPD)from dry powder inhalers (DPIs). Particularly the presence ofa certain amount of lactose fines and smooth, clean carriersurfaces are believed to have a positive effect on drug redispersionduring inhalation.Methods: Adhesive mixtures were prepared with budesonideand different marketed carrier products from differentmanufacturers, having different particle size distributions,and tested upon FPD from two different DPI concepts, havingdifferent de-agglomeration principles, at 4 kPa. FPDs wererelated to different carrier properties to investigate whetherthe claims and suppositions made in literature regarding theeffects of these properties are irrefutably true.Results: The effects of carrier size distribution, carriersurface payload, the amount of lactose fines and surfacerugosity on FPD in this study appeared to depend on thetype of DPI concept used. In a number of examples the effectswere even opposite for the two different DPIs used.Conclusions: The findings underline the hypothesis that parametersand variables relevant to drug re-dispersion from adhesivemixtures during inhalation interact with each other. Theeffect of any of these parameters on FPD may depend on thechoicesmade for the others, as for the choice of DPI in this study.It can be shown that the effect of variations in carrier propertieson FPD may widely be eliminated by using an effective (e.g.classifier based) de-agglomeration principle, as in the Novolizer