Micronized drugs, as used in dry powder inhaler formulations, are very cohesive. For that reason larger carrier particles, commonly α-lactose-monohydrate, are added to improve the de-agglomeration of the powders during inhalation. Different lactose qualities will result in a varying de-agglomeration behavior. Beside the state of surface, the particle size and the surface area it is assumed that amorphous structures may have an influence on the powder performance. Such amorphous parts in the carrier lactose can be brought in during processing the lactose.
In this study the influence of added ball milled amorphous lactose to powder blends containing budesonide and salbutamol sulphate in different concentrations on the de-agglomeration behavior was investigated. The fine particle fraction was investigated after storage at 45% and 75% RH. The fine particle fraction was lower when storing the powders at 75% RH. It could be observed, that the humidity had a greater influence on the powder containing the hydrophilic salbutamol sulphate. For all powders an increase in the fine particle fraction could be observed when adding 5% milled amorphous lactose. This effect was also greater for the powder blends containing salbutamol sulphate than for the blends with budesonide. A higher concentration of salbutamol
sulphate leads to a higher fine particle fraction, for both, the powder blend with 5% amorphous lactose and the blend without amorphous content. In summary, adding milled amorphous lactose increases the fine particle fraction of the powder. The differences are greater for the hydrophilic salbutamol sulphate and also the storage conditions seem to be more important for the hydrophilic drug.