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Particle size distribution (Granulometry)

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Description of key information

Volume Median Diameter = 72.6 µm - 82.7 µm

Cumulative distribution:

< 105 µm : 69.84 - 74.26 %

< 11 µm : 6.76 - 16.59 %

< 4.5 µm : 1.73 - 7.37 %

Additional information

One reliable study is available on granulometry. In this study, the particle size distribution of a typical batch has been determined using laser diffraction particle size analysis to give the volume median diameter (VMD) and the volume size distribution.

Three sub-samples were collected and tested to check variation within the batch:

one near the start of the spray dried batch;

one near the middle of the batch;

one near the end of the batch.

 

The VMD was found to range from 72.6 µm at the beginning of the batch to 82.7 µm at the end of the batch. Approximately 70% of particles are found to be in the inhalable fraction (<100μm).

 

The results from the sampling regime, suggest that there may be less fine material towards the end of the process batch, than found at the start.

 

The fraction less than 11μm, which relates to the thoracic fraction, was found to be 16.6% of the volume at the start of the production batch, and 6.8% near the end. The fraction less 4.5μm, which relates to the respirable fraction, was found to be 7.4% of the volume at the start of the production batch, and 1.7% from the sample collected near the end of the batch.

 

This study was not performed according to a test guideline, but the equipment used is relevant for this endpoint and the samples analysed are representative of the batches manufactured. Therefore, this study is considered as reliable with restrictions.