Understanding Micro Environmental Thermodynamics of Tablet Coating Process Using Data Logger ? Case Studies

Pharmaceutical film coating process is typically monitored by inlet and exhaust temperature and humidity conditions , with measurement devices located outside the coating pan. Current configurations of coating pans does not allow continuous measurement of the temperature and humidity within the tablet bed. Measurable differences in heat and mass transfer efficiencies across coating pan sizes and designs can result in different drying and film forming dynamics at the same measured outlet temperature and humidity. Similarly , different microenvironment (temperature and humidity conditions inside the tablet bed) and hence film forming dynamics can be expected for coating operations carried out at the same exhaust temperature , if this temperature is achieved by changes to the process parameters such as inlet air volume , air temperature , suspension spray rate or suspension solids concentration. Considerable insight into the dynamics of the coating process can be gained if data loggers can be incorporated in the tablet bed and placed such that they can collect temperature and humidity conditions in the tablet bed continuously. Two case studies will be presented where the micro-environmental data from PyroButtons provide meaningful correlation to coated tablet defects. The authors will show that this data can be used to establish a process design space for a given coating and tablet formulation. The first case study is a full factorial design of experiments (DOE) on three process parameters; exhaust temperature , pan speed and spray rate conducted on a 24 inch pan coater , that showed correlation of micro environmental conditions to coated tablet appearance. The second case study will show correlation between delamination tendency of a bilayer tablet and tablet-bed micro environment.