The aerodynamic assessment of the fine particles of inhalation powders is labour-intensive. Therefore, two automated methods for two inhalation products were successfully developed and validated. For maximal flexibility, automated and already existing manual methods should be interchangeable. To assure interchangeability, we aimed to demonstrate their comparability. Together with Novi Systems Ltd,1 a system for automated determination of the aerodynamic particle size distribution (APSD) was developed (Novi Ictus) and customised to handle the Genuair® inhaler, a multi-dose, breath-actuated dry powder inhaler (DPI) developed by Almirall S.A.2 The products used in the study were inhalation powders with active pharmaceutical ingredient (API) combinations (LABA/ICS; LAMA/LABA). For the automated methods, minimal preparation work was necessary. Once the Novi Ictus analysis was complete, the sample solutions were directly transferred to HPLC analysis. The manual methods included the usual equipment preparation, dosing the inhalers, disassembly and extraction of the impactor, as well as cleaning and reassembly. Validated HPLC methods were used for the automated and respective manual methods. The absolute differences between the mean total doses and the differences of the mean FPD of both methods fulfilled the predefined acceptance criteria. RSDs of the FPD and of the total dose seemed to be slightly higher for the automated method but all values met the acceptance criteria. Even though all ratios of the mean total doses and the mean FPD indicated a bias towards higher results for the automated methods, the ratios also fulfilled the acceptance criteria. Hence, this study successfully demonstrated the comparability of the manual and automated methods.
