Exploring the impact of sample flowrate on in vitro measurements of metered dose inhaler performance

D. A. Lewis, H. O'Shea, T. K. Church, G. Brambilla, D. Traini, P. M. Young

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)
26 Downloads (Pure)


Pharmacopoeial methods for measurement of the aerodynamic particle size distribution (APSD) of metered dose inhalers (MDIs) by cascade impaction specify a sampling flow rate of 28.3 L/min. However, there is little data within the literature to rationalize this figure, or to support its clinical relevance. In addition, the standard United States Pharmacopoeia Induction Port (USP IP) used for testing is known to inaccurately reflect deposition behavior in the upper airway, further compromising the relevance of testing, for product development.

This article describes experimental studies of the effect of sampling flow rate on APSD data gathered using an Andersen Cascade Impactor (ACI). Tests were carried out using two different formulations to assess the influence of formulation composition. In addition, comparative testing with an Alberta Idealised Throat, in place of the USP IP, to ensure more realistic representation of the upper airway.

The results show how measured APSD and fine particle dose, the dose than on the basis of size would be expected to deposit in the lung, vary as a function of test methodology, providing insight as to how the testing can be modified towards greater clinical relevance.
Original languageEnglish
Pages (from-to)420-427
Number of pages8
JournalInternational Journal of Pharmaceutics
Issue number2
Publication statusPublished - 5 Dec 2016
Externally publishedYes

Bibliographical note

Copyright the Author(s) 2016. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • Metered dose inhalers
  • Aerodynamic particle size distribution
  • Fine particle dose
  • Testing conditions
  • Cascade impactor
  • Alberta idealized throat


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