Impact of Formulation Properties On Lubrication of Common Tableting Excipients

A recently-developed lubrication blending model identified formulation-dependent parameters for lubrication sensitivity, β, and lubrication rate constant, γ.  The original study examined binary mixtures of common tableting excipients.  Therefore, there is a need to determine if the lubrication model is applicable for a wider range of solid oral pharmaceutical tablet excipients by observing the impact of formulation properties (i.e. lubricant level, particle size and morphology) on the bulk specific volume and tablet tensile strength of lubricated excipients.  18 excipients were examined this study.  All 18 excipients were evaluated for lubrication sensitivity analysis at a particle sieve cut range of 90-125 microns and 1 wt-% magnesium stearate.  6 excipients were selected for particle size and level of lubrication study and examined using a 2² experimental design with center point.  The previously-developed lubrication model was found to adequately describe the impact of lubrication on tensile strength and bulk specific volume of a wide range of excipients.  γ was similar for bulk specific volume and tablet tensile strength changes for a wide range of excipients, while b exhibited less correlation. Excipient particles with round shapes and smooth surfaces appear to have higher γ values (e.g. spray-dried lactose, γ ~ 10^-2 decimeters^-1), and, therefore, are more quickly lubricated by magnesium stearate, than rough, irregularly shaped particles (e.g. crospovidone, γ ~ 10^-5 decimeters^-1).  γ may also depend on the cross-sectional area of the formulation particles and on the level of lubricant in the formulation.  The results suggest that material properties of the excipients and the lubrication level in the formulation are a significant contributor to the sensitivity of a formulation to lubrication effects.  Further, the results suggest that formulations can be designed to provide reduced sensitivity to adverse effects associated with lubrication, thereby improving the overall robustness and quality of the drug product.