Development Aspects, Physiochemical Characteristics, Pharmaceutical Requirements and Different Manufacturing Procedures for Dry Powder Inhalation Formulations
Dry Powder Inhalation (DPI) products are combination of pharmacologic activity and pharmaceutical properties including procedure used to manufacture. Desirable performance features of DPI are physical and chemical stability, ease of handling, accurate and reproducible delivery to the target organ and availability of drug at the site of action. The physical stability of DPI is of utmost importance as it results in ultimate deposition of drug through various dispersion mechanisms into the lungs from where it acts locally or is absorbed and circulated. This can be achieved by selecting suitable manufacturing procedure under appropriate environmental conditions. This review focuses on development process, manufacturing techniques and various parameters related to the stability and performance of the DPI formulation. Most DPI formulations consist of micronized drug blended with lactose of different particle size as carrier, which enhances flow, reduce aggregation and aid in dispersion. The intrinsic physical and chemical properties, particle size, form, shape, surface area, and morphology affects the forces involved in interaction and aerodynamic behaviour, which in turn determine fluidization, dispersion, distribution of drug to the lungs and deposition in the airways. When a DPI is actuated, the formulation is fluidized and enters the lungs. Inspiratory airflow separates drug particles from the carrier particles and are carried deep into the peripheral airways, while the larger carrier particles impact on the oropharyngeal surfaces and are cleared. If the shear of the airflow is not sufficient to separate the drug from the carrier particles due to strong cohesive forces acting on the powder and may results in low deposition efficiency. The force of adsorption of drug on carrier particles determines the percentage of drug deposition in the lungs.
