Elucidation of the variability in consistency of pharmacopoeia quality petrolatum

Abstract

The Pharmacopeia monograph for petrolatum poorly defines the material's physical properties. Indeed, differences between petrolatum grades can be substantial; yield stress varies between 65 and 280 Pa which can be compared with 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 SiO particles were added to petrolatum. Indeed, a small increase in SiO 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 Pharmacopeia 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.

Mineral oil in food, cosmetic products, and in products regulated by other legislations

“…Semi-liquid paraffin is a blend of solid and liquid qualities, comprising paraffin wax, microcrystalline wax, and a white oil (Barry and Grace 1971;van Heugten et al 2017). Semi-liquid paraffin is also called petrolatum, Vaseline, or petroleum jelly.…”

Scale up of Semisolid Dosage Forms Manufacturing Based on Process Understanding: from Lab to Industrial Scale

“…In order to establish a process window for the ointment filling temperature, additional experiments were conducted. For ointments and creams, it is known that their rheological behavior is complex and highly temperature dependent (8,9). The influence of the filling temperature on the weight variation in filled tubes was determined first (Fig.…”