Evaluation of the Mixing Characteristics of Magnesium Stearate Using Triboelectric Properties

Magnesium stearate (MgSt), which is often used as a lubricant in the production of solid formulations, has different stearic acid and palmitic acid contents depending on the lot and manufacturer, resulting in differences in mixability and lubricating effect. However, there are few reports on the effect of the different physical properties of MgSt samples on mixing and tablet formation. Additionally, it is known that the triboelectric properties of components affect the mixability. Overmixing of formulations can decrease tablet hardness. In this study, the triboelectric properties and mixability of MgSt samples with different lots and manufacturers were evaluated. Tablet hardness was used as an index of the mixability of the MgSt samples with various excipients. The triboelectric properties of the MgSt samples depended on the production lot. Mixability was higher when the triboelectric properties of the excipient and MgSt were different. By evaluating the charge properties of MgSt, it should be possible to select the optimum lot and manufacturer of MgSt for specific formulations.