ABSTRACT
A. Overview of Coating Processes A comprehensive overview of pharmaceutical coating (materials, formulations, and processes) has been given by Porter and Bruno [1]. It should be noted that there has been a steady transition in the pharmaceutical industry, beginning with sugar coating, moving to film coating, and finally arriving at aqueous film coating. Sugar coating can be characterized as a relatively complex but noncritical process. Complexity stems from the multiplicity of coating formulations used during one process and the sequencing (dosing, distributing, and drying) that must take place for each application of coating liquid; noncriticality is associated with the fact that precise control over process parameters (air volumes, temperatures, spray rates, etc.) is not a prerequisite for success in the process. In contrast, film coating is relatively simple but critical process. In this case, simplicity relates to the need to use fewer (and sometimes only one) coating formulations during the process, which are usually applied in a continuous but controlled manner; criticality is manifest by the need to identify and control a range of key processing factors, especially when applying water-based coating formulations.
