Understanding the thermodynamic micro-environment inside a pan coater using a data logging device

Abstract

This study showed that PyroButtons can provide very meaningful micro-environmental data that can be correlated to coating defects, and can aid in establishing a process design space for a given coating and tablet formulation.

Influence of Process Parameters on Tablet Bed Microenvironmental Factors During Pan Coating

“…The average tablet bed T for run A was 40.3°C, which is lower than the target exhaust temperature of 44°C. These data show that the temperature experienced by the tablets was cooler than the exhaust temperature and are in agreement with previous reports in the literature (18,21). The average tablet bed RH during the steady spraying phase for run A was 26.3%.…”

“…At one extreme, a high spray rate may cause coating defects such as twinning, picking and sticking, and logo bridging (18), whereas at the other extreme, a low spray rate may cause spray drying and a loss in coating efficiency. Spray rates are especially important if the tablet formulation or API is moisture-sensitive as residual water content in the coated tablets has been shown to be directly related to the spray rate (12).…”

“…Later studies using infrared gun measurements, however, showed that the tablet bed temperature is generally 2-3°C cooler than the exhaust air temperature. In more recent studies utilizing PyroButtons (17,18,21), the exhaust temperature was shown to be up to 10°C higher than the tablet bed temperature, and the magnitude of the difference was a function of the process conditions and batch size. In the absence of tablet bed temperature data, the exhaust temperature provides a rough estimate of the tablet bed temperature.…”

“…It was shown that controlling tablet bed humidity was critical for coated product quality for a tablet core/coating system combination with a narrow process design space. In separate studies, a strong correlation was established between the tablet bed RH and tablet defects such as logo bridging and bilayer tablet delamination rates on accelerated stability (18,20).…”

“…Pandey et al (17,18) have shown the utility of PyroButton data (temperature and humidity) logging devices in obtaining information regarding the thermodynamic microenvironment experienced by the tablets during the coating process. These tablet-sized devices (16-mm diameter) were secured at specific locations in the equipment and placed in the tablet bed and allowed to tumble freely along with the tablets (17)(18)(19). The tablet bed relative humidity (RH), as measured by PyroButtons moving freely with the tablets, was found to be a more sensitive response compared to conventionally monitored process variables.…”