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16 May/June 2021 Tablets & Capsules 5. K. E. Wilson and E. Crossman, "The influence of tablet shape and pan speed on intra-tablet film coating uniformity," Drug Development and Industrial Pharmacy, 1997, Vol. 23, No. 12, pages 1,239-1,243. 6. C. Cunningham, J. Hansell, F. Nuneviller III, and A. R. Rajabi-Siahboomi, "Evaluation of recent advances in continuous film coating processes," Drug Development and Industrial Pharmacy, February 2010, Vol. 36, No. 2, pages 227-233. 7. C. Cunningham, J. Crönlein, and O. Nohynek, "Evaluation of a continuous-cycled film coater in apply- ing a high-solids coating formulation," Tablets & Capsules, October 2015. 8. S. Just, G. Toschkoff, A. Funke, D. Djuric, G. Scharrer, J. Khinast, K. Knop, and P. Kleinebudde, "Optimization of inter-tablet coating uniformity for an active coating process at lab and pilot scale," International Journal of Pharmaceutics, November 2013, Vol. 457, No. 1, pages 1-8. 9. C. Cunningham, C. Neely, A. Birkmire, E. Anderson, and A. Rajabi-Siahboomi, "Enhanced intra-tablet coat- ing uniformity in the ConsiGma coating process," Poster T1330-11-083, AAPS PharmSci 360, Washington DC, November 2018. 10. K. Klop, and P. Kleinebudde, "PAT-tools for process control in pharmaceutical film-coating applications," Inter- national Journal of Pharmaceutics, December 2013, Vol. 457, No. 2, pages 527-536. 11. C. V. Möltgen, T. Puchert, J. C. Menezes, D. Loch- mann, and G. Reich, "A novel in-line, NIR spectroscopy application for the monitoring of tablet film coating in an industrial scale process," Talanta, April 2012, Vol. 92, pages 26-37. 12. M. Haaser, K. C. Gordon, C. J. Strachan, and T. Rades, "Terahertz pulsed imaging as an advanced char- acterization for film coatings—A review." International Journal of Pharmaceutics, December 2013, Vol. 457, No. 2, pages 510-520. 13. D. Markl, G. Hannesschläger, S. Sacher, M. Leitner, and J. G. Khinast, "Optical coherence tomography as a novel tool for in-line monitoring of a pharmaceutical film-coating process," European Journal of Pharmaceutical Sciences, May 2014, Vol. 55, pages 58-67. 14. M. Choi, S. C. Porter, B. Macht, and A. Meisen, "Novel coating uniformity models for tablet pan coaters," AAPS PharmSciTech, November 2020, Vol. 22, No. 7, pages 1-17. Stuart C. Porter, PhD, is president of PPT Pharma Tech- nologies (215 853 4137, sporterpt@aol.com). He is also a member of Tablets & Capsules' technical advisory board. [11] have shown how NIR can be useful as an extremely sensitive tool for monitoring a pan-coating process in real time, with a focus on determining the coating uniformity. Haaser, et al. [12] have provided a review of the applica- tion of terahertz imaging techniques for monitoring both inter- and intra-tablet coating variability as well as coating structure. One limitation relates to reduced accuracy at low tablet weight gains, so this application is more appropriate for monitoring the application of modified-release coatings, where weight gains are typically higher. Finally, Markl, et al. [13] have shown how optical coherence tomography is a useful technique for monitoring film-coating processes, with similar benefits to terahertz analysis in terms of scope but without the limitation of inaccuracy at low weight gains. However, it does require the coating to be somewhat trans- parent, so it is not useful for monitoring the application of opacified, pigmented film coatings. The application of such in-line PAT tools to batch coating processes can be challenging (though many of these chal- lenges can be overcome), but their application to continuous coating processes may prove simpler. The availability of PAT tools for in-line monitoring of coating processes provides great value to pharmaceutical scientists and process engineers. However, there is potential value in having access to tools that can study the variables inherent in a coating process and make predictions relating to process conditions that could minimize coating variabil- ity. One example, suitable to both batch and continuous coating processes, has recently been described by Choi, et al. [14] and focuses on the design of novel coating unifor- mity models for tablet pan coaters. Access to tools of this nature facilitate the design of coating processes capable of achieving important quality attributes during the early stages of product development and can ultimately simplify the scale-up process. As these advancements show, continuous film-coating processes have come a long way from their limited humble beginnings over three decades ago and are positioned to play a key role in modern pharmaceutical manufacturing. Almost certainly, these technologies will continue to advance as the needs of the global pharmaceutical industry continue to evolve. T&C References 1. S. C. Porter, "Continuous film coating processes: A review," Tablets & Capsules, April 2007. 2. J. Marjeram, "Advantages of continuous pharmaceutical tablet coating," Tablets & Capsules, April 2011. 3. C. Cunningham, J. Crönlein, O. Nohynek, and A. Rajabi-Siahboomi, "Simultaneous application of a two-part delayed release coating in a single pass continuous coating process," Poster #44, CRS Annual Meeting & Exposition, New York, July 2018. 4. N. Hampel, A. Bück, M. Peglow, and E. Tsotsas, "Con- tinuous pellet coating in a Wurster fluidized bed process," Chemical Engineering Science, February 2013, Vol. 86, pages 87-98.