(17b) The Influence of Imperfect Geometric Scaling on Inter-Tablet Coating Variability

Wassgren, C. R., Purdue University
Kumar, R., Purdue University

Due to the complexity of the unit operation, batch pharmaceutical coating is usually performed at various scales with the intention of using results from one scale to improve the operation at the next.  Unfortunately, full similarity between scales of all of the important factors impacting coating is difficult, if not impossible to achieve.  In this talk, we investigate the influence that imperfect geometric scaling has on inter-tablet coating variability.  In particular, because the same size tablets are used at various scales, the ratio of the coating pan size (D) to the tablet size (d) does not remain constant between scales.  We observe, similar to previous researchers, that the speed of tablets at the free surface increases with increasing D/d.  Furthermore, coating variability also increases as D/d increases.  We discuss the implications of these results for scaling coating operations.