Surface effects in dry powders for inhalation

Dry powder inhalers (DPI) build the fundament of anti-inflammatory therapy for respiratory diseases like asthma and COPD. To reach the target tissue in the lung, the drug particles need to be micronised (< 5 µm), or at least have a corresponding flight behaviour. Particles in that size range come with detrimental properties like high cohesiveness and increased electrostatic charge. Hence, the pure drug is hard to handle, and reproducible dose metering is impossible. Consequently, the drug needs excipients to form a suitable formulation. The most common one is the interactive blend, also referred to as adhesive mixture. It bases on a drug carrier with micronised drug adhering on its surface. 

Such formulations suffer insufficient drug detachment, due to excessive adhesion. Adhesion is multifactorial and hard to predict. This work investigates the surface energy of solids as an easily accesible bulk parameter, which influences adhesion. Herewith this thesis covers studies on surface energies of carrier particles and how to modify them in order to improve drug delivery.

Furthermore, fine excipients are within the scope of this work, as performance enhancing additives. Surface energies of such fine excipients influence the resulting performance enhancement. To ease the choice of these additives in formulation development, it was shown that there are optimal combinations of drug and fine excipients in regard to their surface energy. Additionally, modification techniques to adjust surface energies of fine excipients were presented. 






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