Advanced numerical-simulation techniques can aid in the development and optimization of pharmaceutical tablet-coating processes.
Investigating mixing performance and the resulting residence time distribution of different coating apparatus can be used
to increase intra-tablet coating homogeneity. Numerical simulations of the interplay of drying air, spray, and tablet bed
were used to examine both local and global coating performance. Computational results showed how the process parameters influence
the film quality and coating uniformity. A usual rule-of-thumb is to place the nozzle at about one-third of the tablet bed,
measured along the bed surface starting from the top. The study of different spray-nozzle setups showed that in terms of spray
loss, following this rule indeed gave the best results. However, aiming the nozzle slightly away from the air inlet could
reduce the amount of spray loss. Finally, inter-tablet coating variability was quantified by using the DEM method to determine
the effects of tablet flow inside the coater in terms of residence time under the spray.
In addition to helping achieve a mechanistic understanding of the coating process, the computational data can be collected
into in-silico design spaces, in which the correlation between critical process parameters and critical quality attributes provide an improved
understanding of the design, optimization, and operation of industrial coating devices.
Gregor Toschkoff, Daniele Suzzi, PhD, and Siegfried Adam, PhD, are researchers at the Research Center for Pharmaceutical Engineering (RCPE) in Graz, Austria. Johannes Khinast*, PhD, is director of RCPE and head of the Institute for Process and Particle Engineering, Graz University of Technology, Inffeldgasse
21/a/II 8010 Graz, Austria, tel. +43 316 873 7978, email@example.com
*To whom all correspondence should be addressed.
Submitted: Apr. 15, 2011; Accepted: Jan. 16, 2012.
1. A. Kalbag and C. Wassgren, Chem. Eng. Sci.
64 (11), 2705–2717 (2009).
2. D. Suzzi, S. Radl, and J.G. Khinast, Chem. Eng. Sci.
65 (21), 5699–5715 (2010).
3. B. Freireich and C. Wassgren, Chem. Eng. Sci.
65 (3), 1117–1124 (2010).
4. S. Tobiska and P. Kleinebudde, Intl. J. Pharmaceutics
224 (1–2), 141–149 (2001).
5. L. Ho et al., J. Control. Rel., 119 (3), 253–261 (2007).
6. W.R. Ketterhagen, M.T. am Ende, and B.C. Hancock, J. Pharm. Sci.
98 (2), 442–470 (2009).
7. A. Alexander, T. Shinbrot, and F.J. Muzzio, Powd. Tech.
126 (2), 174–190 (2002).
8. G. Toschkoff et al., AIChE J.
58 (2), 399–411 (2012).
9. D. Suzzi et al., Chem. Eng. Sci.
69 (1), 107–121 (2012).