Understanding in-vitro performance of inhaler products

Andy Cooper and Chris Blatchford of 3M group investigate Acoustic methodology for measuring discharge rate, and predicting spray velocity effects on potential lung deposition

Understanding in-vitro performance of inhaler products is still a key factor in understanding or predicting in-vivo performance. Rapid assessment techniques could therefore be useful for increasing the efficiency of early phase product development.

Several potential techniques or diagnostic-type tests are available, such as laser techniques, accelerometers, electrostatic probes, firing force measurements.

This publication will focus on one specific area Acoustic measurement. Actuation duration can be inferred from the sound duration ascertained via acoustic measurements. For comparison of simple pMDI systems this can yield information on spray velocity, a critical characteristic in terms of lung deposition. Data for spray velocity are also presented.

The spray duration trends are compared to those when using numerical modelling of propellant flow inside the pMDI metering valve. The potential effect of different spray durations on lung deposition is then demonstrated via in-vitro APSD data, specifically the emitted dose post-throat (%).

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