Modeling the motion and orientation of various pharmaceutical tablet shapes in a film coating pan using DEM.

Film coating uniformity is an important quality attribute of pharmaceutical tablets. Large variability in coating thickness can limit process efficiency or cause significant variation in the amount or delivery rate of the active pharmaceutical ingredient to the patient. In this work, the discrete element method (DEM) is used to computationally model the motion and orientation of several novel pharmaceutical tablet shapes in a film coating pan in order to predict coating uniformity. The model predictions are first confirmed with experimental data obtained from an equivalent film coating pan using a machine vision system. The model is then applied to predict coating uniformity for various tablet shapes, pan speeds, and pan loadings. The relative effects of these parameters on both inter- and intra-tablet film coating uniformity are assessed. The DEM results show intra-tablet coating uniformity is strongly influenced by tablet shape, and the extent of this can be predicted by a measure of the tablet shape. The tablet shape is shown to have little effect on the mixing of tablets, and thus, the inter-tablet coating uniformity. The pan rotation speed and pan loading are shown to have a small effect on intra-tablet coating uniformity but a more significant impact on inter-tablet uniformity. These results demonstrate the usefulness of modeling in guiding drug product development decisions such as selection of tablet shape and process operating conditions.