A clinically more relevant approach for comparing the aerodynamic particle size distribution (APSD) of a generic dry powder inhaler (DPI) to that of an originator has been proposed, which could potentially replace an EU standard. This article describes the results of a study that follows these principles for APSD in vitro bioequivalence (IVBE) assessment of three tiotropium DPIs.
The proposed approach should be more relevant, not only since it uses a test method better mimicking the way a patient uses the product, but also because products are compared based on a mix of data obtained under different realistic conditions. This approach therefore follows the general philosophy for comparing treatments used in standard clinical testing. A further advantage is that the potential effects by peak inspiratory flow rate (PIFR), acceleration (time to PIFR, TPIFR) and inhalation time (T), can be individually estimated, thus allowing deeper understanding of device and formulation characteristics for both products studied.