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. 2014 Feb;15(1):65-74.
doi: 10.1208/s12249-013-0036-0. Epub 2013 Oct 3.

The effect of moisture on the flowability of pharmaceutical excipients

Allison Crouter  1 , Lauren Briens
Affiliations

The effect of moisture on the flowability of pharmaceutical excipients

Allison Crouter et al. AAPS PharmSciTech. 2014 Feb.

Abstract

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.

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Figures

Fig. 1
Fig. 1
Schematic diagram of the humidity chamber
Fig. 2
Fig. 2
Particle size distributions of the powders
Fig. 3
Fig. 3
Scanning electron micrographs of the powders
Fig. 4
Fig. 4
Moisture adsorption isotherms of the tested powders
Fig. 5
Fig. 5
Avalanche times and standard deviations for a MCC, b CMC, c HPMC, d PVP, e corn starch, and f potato starch
Fig. 6
Fig. 6
Dynamic density measurements of a the celluloses and PVP and b the starches
See this image and copyright information in PMC

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