AAPS PharmSciTech

, Volume 15, Issue 1, pp 65–74 | Cite as

The Effect of Moisture on the Flowability of Pharmaceutical Excipients

  • Allison Crouter
  • Lauren Briens
Research Article


The effect of moisture content on flowability of six pharmaceutical powders (microcrystalline cellulose (MCC), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), corn starch, and potato starch) was investigated. Powder flowability was measured using established static techniques and emerging dynamic avalanche behavior measurements. Static techniques did not provide enough resolution to clearly identify changes in flowability due to increasing powder moisture content. Avalanche time and its standard deviation showed that flowability of MCC, CMC, PVP, and potato starch decreased after a critical moisture content, flowability of corn starch increased and flowability did not significantly change for HPMC. The moisture decreased flowability by forming stronger interparticle liquid bridges and increased flowability by acting as a lubricant. The dynamic density of the celluloses and PVP decreased linearly with increasing moisture content as the particles swelled with water. The starches also swelled and decreased in dynamic density, but only after a moisture content corresponding to monolayer coverage of water around the particles was reached. As flowability and dynamic density change with moisture content, to ensure consistent production of high-quality tablets, the moisture content of the powders must be measured and controlled.


adsorption isotherms avalanche behavior flowability moisture content pharmaceuticals 



The authors would like to acknowledge the financial support of the Natural Sciences and Engineering Council of Canada (NSERC) and support through Ontario Graduate Scholarships (OGS) for Allison Crouter. Kylie O’Donnell is also acknowledged for her work on the preliminary trials of this study.


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Copyright information

© American Association of Pharmaceutical Scientists 2013

Authors and Affiliations

  1. 1.Chemical and Biochemical Engineering, Faculty of EngineeringWestern UniversityLondonCanada

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