What’s next in the use of opacifiers for cosmetic coatings of solid dosage forms? Insights on current titanium dioxide alternatives

The consolidated use of coatings containing E171 (i.e. titanium dioxide, TiO2) as an opacifier has made the white color of the resulting dosage forms a quality standard in the pharmaceutical and dietary supplement fields. This color is also associated with the efficiency of the coating layer in protecting the substrate from the effects of UV rays. However, health risks related to diet exposure to TiO2 has recently been advanced and its addition in coating formulations has been seriously questioned. As a consequence, in principle safer TiO2-free formulations have been recently launched on the market, especially for coatings of dietary supplements. In this work, we evaluated the overall physico-technological characteristics and performance of immediate release tablets coated with a variety of commercial cosmetic formulations free of E171. Moreover, a quantitative method based on the CIELab color space was proposed for the first time for studying the covering/coloring performance of the coating formulations. Based on the results obtained, the possibility to achieve a satisfactory covering capability and a degree of white comparable to that of a standard TiO2-containing reference with all the commercially-available ready-to-use TiO2-free products considered, without affecting the dissolution performance, was demonstrated.