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Impact of Processing Conditions on Inter-tablet Coating Thickness Variations Measured by Terahertz In-Line Sensing.

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Lin, Hungyen 
May, Robert K 
Evans, Michael J 
Zhong, Shuncong 
Gladden, Lynn F 


A novel in-line technique utilising pulsed terahertz radiation for direct measurement of the film coating thickness of individual tablets during the coating process was previously developed and demonstrated on a production-scale coater. Here, we use this technique to monitor the evolution of tablet film coating thickness and its inter-tablet variability during the coating process under a number of different process conditions that have been purposefully induced in the production-scale coating process. The changes that were introduced to the coating process include removing the baffles from the coater, adding uncoated tablets to the running process, halting the drum, blockage of spray guns and changes to the spray rate. The terahertz sensor was able to pick up the resulting changes in average coating thickness in the coating drum and we report the impact of these process changes on the resulting coating quality.



Processing, Unit operations , coating, imaging methods, physical characterization, process analytical technology (PAT), quality by design (QBD), tablet, Automation, Chemical Phenomena, Drug Compounding, Electrochemical Techniques, Image Processing, Computer-Assisted, Quality Control, Reproducibility of Results, Surface Properties, Tablets, Enteric-Coated

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J Pharm Sci

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Elsevier BV
Engineering and Physical Sciences Research Council (EP/L019922/1)
This work was conducted with financial support from the UK Technology Strategy Board (AB293H). H.L. And J.A.Z. would like to acknowledge the Engineering and Physical Sciences Research Council (EP/L019922/1) and the Newton Trust Cambridge for research funding. J.A.Z. would like to thank Gonville & Caius College, Cambridge for a research fellowship. The authors acknowledge Colorcon Ltd. and Meggle AG for providing the excipients used in this study, Provel Ltd. (Bolton, UK) for the kind loan of the mixing equipment to disperse the coating polymer and Staffan Folestad (AstraZeneca) for useful discussions. Additional data related to this publication is available as a supplementary data to this publication as well as at the University of Cambridge data repository (