Further development of an image analysis approach for the quantification of emitted agglomerates from suspension-based pressurised Metered Dose Inhalers

P A Jinks

In order to design pressurised Metered Dose Inhalers (pMDIs) that deliver their medication on target, it is important to understand the factors that may give rise to dosing variation. One such factor is the emission of agglomerates, in particular from pMDIs formulated as suspensions. This paper builds on previous work in developing methodology to quantify the emission of agglomerates in the emitted dose of pMDIs using an image analysis technique. In the new methodology, composite images were created by the use of an automated microscope stage to allow greater image resolution and a wider scan area to encompass the whole sample. The technique was then applied to a marketed suspension product, available as three different strengths to explore the effect of product strength of the emission of agglomerates through unit life. It was found that there was significant upward trending in agglomerate emission for each of the three tested product strengths, in particular between the start and the middle of life shots. The overall level of agglomerate emission as determined by total agglomerate area was however found to be of a similar order of magnitude across the product strengths.  The latter finding would suggest that agglomerate emission may be a more significant factor in affecting the dosing consistency of lower dose suspension products where the impact of a given mass of emitted agglomerates in the emitted dose, will be proportionately greater. Finally it is recommended that agglomerate emission should be minimised during system design by the appropriate use of formulation adjuvants or release coatings on the hardware components to minimise deposition.


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