Coating of particulates by bottom-spray air suspension processes

Abstract

Air suspension coating of particulates is an important pharmaceutical process. Coating of fine particulates is challenging due to their high propensity for agglomeration. In this study, coating equipment, process parameters, core particles and coating materials were studied to investigate the conditions favourable for coating. The performance of two bottom-spray air suspension coaters, Wurster and Precision coaters, were assessed. The Precision coater showed better coating performance due to faster and better separation of pellets moving through the spray zone. Both fluid dynamics and thermodynamics were important in affecting the quality of coated pellets. Based on the findings obtained, fine lactose particles were coated with hypromellose solution. Calcium carbonate nanoparticles, when used either as a surface-modifying agent for lactose or an anti-tack additive in hypromellose solution, were found to reduce the agglomeration of lactose to varying degrees by different mechanisms. This study enabled better understanding of conditions favourable for coating fine particulates.