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Real-Time Monitoring of Thermodynamic Microenvironment in a Pan Coater

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ABSTRACT

The current study demonstrates the use of tablet-size data logging devices (PyroButtons) to quantify the microenvironment experienced by tablets during pan coating process. PyroButtons were fixed at the inlet and exhaust plenums, and were also placed to freely move with the tablets. The effects of process parameters (spray rate and inlet-air humidity) on the thermodynamic conditions inside the pan coater were studied. It was shown that the same exhaust temperature (a parameter most commonly monitored and controlled during film coating) can be attained with very different tablet-bed conditions. The tablet-bed conditions were found to be more sensitive to the changes in spray rate as compared with the inlet-air humidity. Both spray rate and inlet-air humidity were shown to have an effect on the number of tablet defects (loss of logo definition), and a good correlation between number of tablet defects and tablet-bed humidity was observed. The ability to quantify the thermodynamic microenvironment experienced by the tablets during coating and be able to correlate that to macroscopic tablet defects can be an invaluable tool that can help to establish a process design space during product development. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:336–340, 2013

Section snippets

INTRODUCTION

Film coating of tablets is a frequently used unit operation in the pharmaceutical industry. The coating applied can either be nonfunctional (aesthetic) or functional (controlled-release or active coating, etc.) and is performed either in a pan or a fluid-bed coater.1 In pan coating, a batch of tablets gets sprayed on with an atomized coating suspension over a period of time as hot air passes through a cascading layer of tablets. The process parameters of most interest include pan load, pan

MATERIAL AND METHODS

Placebo formulation consisting mainly of microcrystalline cellulose (FMC Company,Philadelphia, Pennsylvania), lactose anhydrous (Kerry Bio-Sciences, Norwich, New Jersey), croscarmellose sodium (FMC Company), and magnesium stearate (Mallinckrodt Chemicals, Saint Louis, Missouri) was compressed into debossed oval-shaped tablets at a target press weight of 200 mg. The formulation of the core tablets consisted of a relatively high amount of magnesium stearate (1.25%, w/w). The tablets were coated

RESULTS

Typical temperature (T) and RH data set obtained from PyroButtons are shown for run #1 in Figures 2 and 3, respectively. The exhaust PyroButton (Opulus) data shown in Figure 2 confirm the exhaust temperature of 44°C. The two freely moving PyroButtons show comparable data to each other, demonstrating good repeatability of the measurement. The data for freely moving PyroButtons show more fluctuations (both T and RH) than the fixed PyroButtons due to their dynamic motion and varying location

CONCLUSIONS

This study demonstrated the utility of PyroButtons in providing a detailed thermodynamic picture of the coating process. It was shown that same exhaust temperature, the most commonly controlled and monitored parameter during coating process, can be attained under different conditions of the tablet bed. This difference in tablet-bed thermodynamic conditions can then result in a different final product quality (visual appearance in this case). The tablet-bed RH was found to be a more sensitive

ACKNOWLEDGEMENTS

The authors would like to thank Elena Zour from Bristol-Myers Squibb and Bela Jancsik from Opulus® for their help and support during this work.

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