A Collaborative Study by the European Pharmaceutical Aerosol Group (EPAG) to Assess the Flow-Time Profile of Test Equipment Typically Used for pMDI/DPI testing – Part 2: Flow-Time Profile testing

R Greguletz, P Andersson, J Arp, C Blatchford, G Daniels, V Glaab, M Hamilton, M Hammond, J Mitchell, D Roberts, C Shelton, A Watkins (on behalf of EPAG)

Background: We report here on the second of a two-part study aimed at characterizing and assessing the flow-time profiles of typical test equipment used for pressurised metered dose inhaler/dry powder inhaler (pMDI/DPI) products. The main objective was to generate flow-time profile data descriptive for typical test setups and sampling units and that may be useful for comparison. Methods: The measurement method used a thermal mass flow sensor and a proprietary flow recording software to store and assess recorded flow-time data sampled at the inlet of test systems (TS), cascade impactors (CI), and sample collection tubes (SCT) for delivered dose testing. Three orifices were used to simulate a typical range of DPI device resistance by generating a pressure drop of approximately 4 kPa at the respective test flow rates. Flow profiles that result from a defined air flow time of 4 sec at different air flow rate levels were measured. Results: Ninety-two experimental arrangements across nine companies were examined and a total of 815 individual flow profile measurements were performed. Various total air flow volumes, flow peaks, rise times and slope values per flow level of 30, 60, and 90 L/min were determined for different TSs, CIs, and SCTs. Rise time t90% (with 4 kPa orifice at inlet side) showed the following order: NGI>ACI>AIM>SCT>TS. Conclusions: The results demonstrated that the experimental methods were both straightforward and precise. A broad data base of flow-time data descriptive for compendial equipment as typically used in the industry for pMDI/DPI testing was established.

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