Alternatives to titanium dioxide in tablet coating

Abstract

Titanium dioxide (TiO₂) is one of the most commonly used pharmaceutical excipients. It is widely used as a white pigment in tablet and pellet coatings. However, it has recently been under massive criticism as a number of studies suggest a cancerogenic potential. It can therefore no longer be taken for granted that TiO₂ will continue to be universally available for drug products. Finding suitable alternatives is hence of special relevance. In this study, a number of different pigments were coated on tablets and their covering potential analyzed. None of the alternative pigments showed comparable effectiveness and efficiency to TiO₂, though the CaCO₃/CaHPO₄-based coating showed the second-best results. Regarding the ability to protect photosensitive active ingredients, ZnO showed a comparable potential as TiO₂, while all other pigments failed. Using the alternative pigments as markers for in-line Raman spectroscopy as a process analytical technology was challenging and led to increased prediction errors. Again, the CaCO₃/CaHPO₄-based coating was the only of the tested alternatives with satisfying results, while all other pigments led to unacceptably high prediction errors.

Keywords:

• Titanium dioxide
• tablet coating
• white pigments
• Raman spectroscopy

Acknowledgments

The authors thank Rok Sibanc, who developed the software for color analysis of the coated tablets. Furthermore, the authors extend our appreciation to BASF and Biogrund for providing the excipients as well as L.B. Bohle for providing the tablet cores.

Disclosure statement

No potential competing interest was reported by the authors.