The impact of solid-state form, water content and surface area of magnesium stearate on lubrication efficiency, tabletability, and dissolution

Abstract

Magnesium stearate (MgSt) is a widely used pharmaceutical lubricant in tablet manufacturing. However, batch-to-batch variability in hydrate form and surface area can lead to inconsistency in tablet performance. In this work, several unique MgSt samples were studied: traditional monohydrate samples with high surface area, dihydrate forms with high and low surface area, and disordered forms with low and medium water content. The effects of solid-state form and particle properties on lubrication efficiency, tabletability and dissolution were studied for tablets in a model direct compression formulation. It was found that the monohydrate and dihydrate forms had good lubrication efficiency compared to the disordered form, while the disordered form had the best tabletability. The dissolution rate correlated with surface area, where slower dissolution rates corresponded with higher MgSt surface areas. The dihydrate sample with lower surface area had the best performance for this model formulation, in terms of lubrication efficiency, tabletability and dissolution. Overall, it is concluded that the choice of the most appropriate grade of MgSt for a particular formulation depends on a comprehensive evaluation of the impact of MgSt properties on lubrication efficiency, tabletability and dissolution.

Keywords:

• Magnesium stearate
• lubrication
• ejection force
• dissolution
• tensile strength
• solid-state NMR
• compaction

Acknowledgements

The authors would like to thank Carl Huetteman for valuable discussions and assistance editing this paper. JLC was funded by a Pre-Doctoral Fellowship in Pharmaceutics from the PhRMA Foundation. The authors would also like to thank NSF I/UCRC Center for Pharmaceutical Development (IIP-1063879, IIP-1540011 and industrial contributions) forfinancial support. Additionally, this material is based upon work supported by the National Science Foundation under Grant No.Grant No. 1710453.

Disclosure statement

EJM is a partial owner of Kansas Analytical Services, a company that provides solid-state NMR services to the pharmaceutical industry. The results presented here are from academic work at the University of Kentucky and no data from Kansas Analytical Services is presented here.