Performance-Modifying Influences in Dry Powder Inhalation Systems

Abstract

Although dry powder inhaler (DPI) systems offer many advantages over conventional pressurized metered dose aerosols for therapeutic use, there are a number of formulation-related aspects of functionality which can significantly reduce DPI performance. A general introduction is provided to the physical requirements for preparation of efficient and effective therapeutic aerosols and dry powder inhaler systems in particular. Of a number of important DPI design factors highlighted in the introduction, the present study concentrates on two specific ex vivo performance-modifying influences of particle characteristics used in dry powder inhalers. Firstly, powder entrainment characteristics were studied using a model system and it was found that particle-entrainment tube (device) interactions were of two main types, depending on whether coarse or fine lactose particles were involved. In the case of coarse particles (in the range 90–180 μm), entrainment was found to depend on mean linear air velocity (in the range...