Evaluating the effect of coating equipment on tablet film quality using terahertz pulsed imaging

European Journal of Pharmaceutics and Biopharmaceutics,
http://dx.doi.org/10.1016/j.ejpb.2013.03.019

Authors: Miriam Haaser^{a, b, c, 1}, Kaisa Naelapää^{d, 1}, Keith C. Gordon^e, Michael Pepper^{b, f}, Jukka Rantanen^d, Clare J. Strachan^{a, g}, Philip F. Taday^b, J. Axel Zeitler^h, Thomas Rades^{a, d}
a School of Pharmacy, University of Otago, Dunedin, New Zealand
b +TeraView, St. John’s Innovation Park, Cambridge, UK
c Cavendish Laboratory, +Cambridge University Press Education, Cambridge, UK
d Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
e Department of Chemistry, MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, New Zealand
f Department of Electronic Engineering, +UCL, Torrington Place, London, UK
g Division of Pharmaceutical Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
h Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK

Abstract

In this study, terahertz pulsed imaging (TPI) was employed to investigate the effect of the coating equipment (fluid bed and drum coater) on the structure of the applied film coating and subsequent dissolution behaviour. Six tablets from every batch coated with the same delayed release coating formulation under recommended process conditions (provided by the coating polymer supplier) were mapped individually to evaluate the effect of coating device on critical coating characteristics (coating thickness, surface morphology and density). Although the traditional coating quality parameter (weight gain) indicated no differences between both batches, TPI analysis revealed a lower mean coating thickness (CT) for tablets coated in the drum coater compared to fluid bed coated tablets (p < 0.05). Moreover, drum coated tablets showed a more pronounced CT variation between the two sides and the centre band of the biconvex tablets, with the CT around the centre band being 22.5% thinner than the top and bottom sides for the drum coated tablets and 12.5% thinner for fluid bed coated tablets. The TPI analysis suggested a denser coating for the drum coated tablets. Dissolution testing confirmed that the film coating density was the drug release governing factor, with faster drug release for tablets coated in the fluid bed coater (98 ± 4% after 6h) compared to drum coated tablets (72 ± 6% after 6h). Overall, TPI investigation revealed substantial differences in the applied film coating quality between tablets coated in the two coaters, which in turn correlated with the subsequent dissolution performance.


... Terahertz pulsed imaging measurements. A total of six randomly chosen tablets of every batch were imaged individually using the TPI Imaga 2000 (TeraView Ltd, Cambridge, UK) ... 

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