Impact of actuation force on the quality assessment of pressurized metered-dose inhalers.

Objective: To investigate the influence of varied actuation forces on the quality assessment of pressurized metered-dose inhalers(pMDIs).

Methods: Both manual and automatic methods were employed to assess the effects of manual actuation and automatic actuation (with different set actuation forces) on the delivered dose uniformity (DDU), emitted dose per actuation (EDPA), and aerodynamic particle size distribution (APSD) results of pMDIs.

Results: When manual actuation was performed, the discrepancies in the DDU were observed, whereas differences in the EDPA and APSD results were not evident. When utilizing automatic actuation, the results for DDU, EDPA, and APSD all exhibited good uniformity. However, it was observed that inadequate actuation force, insufficient to fully open the valve, resulted in lower outcomes for all the aforementioned parameters. And when the actuation speed is excessively low, it results in a decline in the FPF value.

Conclusions: The process of routine manual testing for DDU in inhalation aerosols, as well as methodology transfer in this field, necessitates meticulous attention to the standardization of operation techniques and actuation forces among diverse experimenters. Furthermore, using automated actuation can avoid variations due to manual operation and achieve good uniformity of results. However, when employing automatic actuation, it is crucial to select an actuation force that effectively ensures complete valve opening, thereby safeguarding the accuracy and reliability of the inhalation aerosol product. This suggests that attention should be paid to patients with limited hand strength (such as children and the elderly) when using aerosols.