Formulation considerations for dry powder inhalers.

The market for inhalable dry powder medication has consistently grown over past years. Targeting the lungs has been recognized to offer several advantages compared with oral application of drugs. The successive development of inhalation products has led to advances in local treatment of different respiratory diseases, but has also demonstrated the possibility to utilize the lungs for systemic drug delivery. Since a dry powder inhalation product is always a combination of drug formulation and inhalation device, the requirements for the development of such a system may be particularly complex. Therefore, this review aims to give an overview of the necessary considerations for a successful dry powder inhaler development.

Capabilities and limitations of using powder rheology and permeability to predict dry powder inhaler performance.

Dry powder inhalers play a major role in today's treatment of various respiratory diseases. A lot of effort has been put into the optimization of a device and the appropriate formulation regarding its local lung deposition. However, the complexity and interactions of different factors governing powder dispersion and, therefore, its inhalable fraction challenge research groups around the world. In the current work, binary lactose blends and adhesive ternary powder mixtures containing additional budesonide fines were produced and analyzed with dispersion measurements on the one hand and permeability and aeration measurements conducted with a powder rheometer on the other hand. By comparing the results of the bulk property and dispersion tests, it was expected to gain a better understanding about the effect of excipient fines addition to an adhesive powder mixture. It could be observed that with permeability testing it was possible to clearly differentiate between different amounts of fines within mixtures. However, no correlation between permeability or aeration test values and drug fine particle fraction could be determined for the observed range. Nevertheless, the use of different characterization techniques led to a clearer understanding about the influence of fines addition to an adhesive mixture. It could be demonstrated that after the surface of carrier crystals had been fully saturated, drug particles got incorporated in more stable fines' agglomerates, which resulted in a decrease in fine particle fraction upon dispersion.