In formulations for inhalation, the importance of achieving the correct particle sizes, both for the API and the carrier (which are each required at different sizes), cannot be underestimated and with a number of equipment options it is essential to consider all aspects of the materials involved and the final product requirements.
Dry-powder inhaler formulations typically comprise a carrier substance and active pharmaceutical ingredient (API). Additives are often required to enhance product properties, such as flowability or to support the mechanical bonding of carrier with API.
The carrier material, typically lactose, represents a high proportion of the final product and is often required to be of coarser particle size in the range of 40–200μm. The API is only a tiny percentage of the inhalable formulation and needs to be of finer particle size, usually in the single micron range. API powders are often cohesive with poor flow properties and are sometimes required in a tight particle size distribution. Consideration must be given to the amorphous content of the API.
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