Quantification of Lubricant Activity of Magnesium Stearate by Atomic Force Microscopy

Abstract

Magnesium stearate (MgSt) is commonly used in pharmaceutical formulations as a lubricant to facilitate tablet release from the die after compression. In this study, we quantify the effect of MgSt on the interaction forces between microcrystalline cellulose (MCC) and steel surfaces. A quantitative approach to better understand the mechanism by which MgSt affects powder performance will assist in improved control and formulation design. We find that the forces between MgSt and steel surface are stronger than the interactions between MgSt itself, between MgSt and an MCC particle, and an MCC particle and a steel surface. These quantitative findings offer an explanation how MgSt facilitates lubrication during tablet ejection.

Keywords:

• atomic force microscopy
• magnesium stearate
• microcrystalline cellulose
• cohesion force

ACKNOWLEDGMENTS

We thank Christine Ortiz for providing the AFM equipment used in this study. We are grateful for the discussions with Lakshman Pernenkil and Samuel Ngai during the preparation of this work. The generous support of the Ernest Solvay Foundation and of the Consortium for the Advancement of Manufacturing of Pharmaceuticals (CAMP) is gratefully acknowledged.