The role of particulates in film coating of pharmaceutical tablets

Abstract

Many pharmaceutical tablets have a coating. This chapter discusses the critical quality attributes of coating liquids, their preparation, and the coating process of the tablets. Moreover, it describes how the requirements can be fulfilled in practice. A coating layer can be applied for many reasons, from cosmetic purposes to advanced drug delivery. A coating liquid generally consists of a polymer, a plasticizer, a colorant or opacifier, and sometimes components to stabilize the coating liquid or to improve wetting of the tablets. In the coating process, the liquid is sprayed onto the tablet cores whilst they are moving. The inlet air ensures drying of the tablets. During this drying phase the polymers coalesce and form a smooth thin layer around the tablet of more or less constant thickness. Good quality of the coating liquid is the basis for well coated tablets. Therefore, the preparation of a coating liquid should ensure a lump free, viscous liquid with a set amount of solids.