Use of a novel modified TSI for the evaluation of controlled-release aerosol formulations. I

When considering the development of potential controlled-release pulmonary drug delivery systems, there is at present no standard method available for the assessment of in vitro drug release profiles necessary to understand h ow the drug might release following deposition in the lungs. For this purpo se, the twin-stage impinger (TSI), apparatus A of the BP, has been redesign ed and tested. This modified TSI was found capable of discriminating betwee n drug release rates from conventional and different dry powder formulation s consisting of model controlled-release excipients, providing information related to (a) drug diffusion properties of controlled-release dry powder b lends with different excipient components and (b) the effect of varying dru g concentration within a given formulation.