Elucidation of the variability in consistency of Pharmacopoeia quality Petrolatum.

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Elucidation of the variability in consistency of Pharmacopoeia quality Petrolatum.

Drug Dev Ind Pharm. 2016 Dec 23;:1-20

Authors: van Heugten AJ, Versluijs-Helder M, Vromans H

Abstract
The Pharmacopoeia monograph for petrolatum poorly defines the materials physical properties. Indeed, differences between petrolatum grades can be substantial; yield stress varies between 65 and 280 Pa which can be compared to the consistency of respectively thin cream or thick ointment. This variation is not only due to differences in composition or refining process but also as a result of different processing; for example, thermal history influences petrolatum structure considerably. Slow cooling of petrolatum resulted in a yield stress of 26 Pa and fast cooling in 79 Pa. X-ray showed that crystallinity was 0.7% for the first cooling case and 1.5% for the second one. Crystallite size was estimated to be 20-50 nm. To investigate if this relatively small difference in crystallinity may induce the difference in consistency, 15 nm SiO2 particles were added to petrolatum. Indeed, a small increase in SiO2 concentration led to a major increase in yield stress. This was argued to be due to the small size of the particles, resulting in a large increase in absolute number of particles. The Pharmacopoeia does not unambiguously define the pharmaceutical excipient petrolatum. As a consequence, the formulator has to take care of selecting the appropriate grade as well as to carefully control the processing of the material in order to achieve a consistent pharmaceutical product.

PMID: 28010136 [PubMed - as supplied by publisher]

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