Formulation and Evaluation of Dry Powder Inhaler

Abstract: This review focuses on the dry powder inhaler (DPI) formulation and development process. Most DPI formulations consist of micronized drug blended with larger carrier particles, which enhance flow, reduce aggregation, and aid in dispersion. A combination of intrinsic physicochemical properties, particle size, shape, surface area, and morphology affects the forces of interaction and aerodynamic properties, which in turn determine fluidization, dispersion, delivery to the lungs, and deposition in the peripheral airways. When a DPI is actuated, the formulation is fluidized and enters the patient’s airways. Under the influence of inspiratory airflow, the drug particles separate from the carrier particles and are carried deep into the lungs, while the larger carrier particles impact on the oropharyngeal surfaces and are cleared. If the cohesive forces acting on the powder are too strong, the shear of the airflow may not be sufficient to separate the drug from the carrier particles, which results in low deposition efficiency. This review thus demonstrates that the successful delivery of dry powder aerosols to the lung requires careful consideration of the powder production process, formulation and inhaler device. The developments and improvements towards high dose powder pulmonary drug delivery are summarized and discussed here. It also throws light on the invention and improvement of novel inhaler devices as well as the further development of formulation principles and new powder engineering methods.