Effect of drug load on the aerosolisation propensity of binary adhesive mixtures for inhalation

The aim of this study was to investigate how the propensity for aerosolisation in binary adhesive mixtures was affected by the drug load, and to determine whether these findings could be linked to different blend states. Binary blends of two different lactose carriers, each with varying size and morphology, were prepared together with budesonide. In vitro aerosolisation studies were conducted at four different pressure drops, ranging from 0.5 to 4 kPa, utilising a Next Generation Impactor. Several dispersion parameters were derived from the relationship between the quantity of dispersed API and the pressure drop. The evolution of the parameters with drug load was complex, especially at low drug loads. While similar responses were observed for both carriers, the range of drug load that could be used varied significantly. The choice of carrier not only influenced the capacity for drug loading but also affected the spatial distribution of the API within the mixture, which, in turn, affected its aerosolisation propensity. Thus, the drug dispersion process could be linked to different configurations of the lactose carrier and budesonide in the blends, i.e. blend states. In conclusion, the study suggests that the concept of blend states can provide an explanation for the complex dispersion process observed in adhesive blends.