How to measure coating thickness of tablets: Method comparison of optical coherence tomography, near-infrared spectroscopy and weight-, height- and diameter gain

P. R. Wahl, A. Peter, M. Wolfgang, J. G. Khinast*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Film coating of pharmaceutical dosage forms, such as tablets and pellets, can be used to tailor the drug release profile. With that regard, a uniform coating thickness of a single tablet (intra-tablet), all tablets (inter-tablet) and subsequent batches (inter-batch) is crucial. We present a method comparison between in-line (optical coherence tomography and near-infrared spectroscopy) and well-established off-line (height-, weight- and diameter-gain) approaches to determining the coating thickness of tablets. We used single tablets drawn during a commercial coating process. Comparing the low intra- and high inter-tablet coating variability indicated that the tablets had a broad distribution of spray zone passes but at a random tablet orientation. Even at the end of the coating process at a mean coating thickness of about 70 µm, the inter-tablet standard deviation was about 9 µm or 13% relative standard deviation. Determining correlations between the methods identified the factors that contribute to the measurement uncertainty and bias for each method. Ultimately, we aimed to establish that in-line methods match or even surpass the conventional off-line reference methods in terms of accuracy and precision of coating thickness measurement.

Original languageEnglish
Pages (from-to)344-352
Number of pages9
JournalEuropean journal of pharmaceutics and biopharmaceutics
Volume142
DOIs
Publication statusPublished - 1 Sep 2019

Keywords

  • Coating variability
  • Film coating
  • Near-infrared spectroscopy (NIR)
  • Optical coherence tomography (OCT)
  • Process analytical technology (PAT)

ASJC Scopus subject areas

  • Biotechnology
  • Pharmaceutical Science

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