Paddle over disk as a dissolution test for orally inhaled drugs: discriminating composite from carrier-based formulations
One of the most important steps with in vitro performance testing of inhalation products is the characterization of the delivery of a given active pharmaceutical ingredient (API) from a specified inhaler using a pharmaceutical impactor, to estimate the actual dose that can potentially deposit on the target site of the lung. However, aerodynamic characterization completely misses the assessment of the drug absorption profile, which depends in great extent on the dissolution of the pharmaceutical dosage form. An ideal dissolution test procedure for inhaled formulations would involve particle classification followed by an evaluation of the dissolution behaviour for the classified drug particles that may deposit at various sites in the respiratory tract.
Son et al. developed a potential standardized test method applicable to various formulations, as a variation of USP Apparatus 2 (paddle), designated paddle over disk apparatus. This method is amenable for inhaled products as particles with a known aerodynamic diameter can be collected using a next generation impactor (NGI) and can be directly positioned inside the vessel, guaranteeing that the tested powder is within the respirable fraction. The present work aims to use the paddle over disk (POD) apparatus to characterize dry powder inhaler (DPI) formulations of composite particles produced by spray drying and blend formulations of API and lactose aimed for pulmonary delivery, specifically.