The Utility of Colorimetry as a Quality Control Tool for the Identification of Pharmaceutical Tablets

There is an ongoing need for new or alternate approaches to identify innovative pharmaceutical products and distinguish them from counterfeit medicines. In this study we present data that demonstrate how quantitative measurement of the color on the surface of tablets could be used to accomplish this objective. Several proof-of-concept studies were performed in which ColorQuest XE colorimeter was used to measure the tristimulus L*, a*, and b* color values from the surface of pharmaceutical tablets. These values represent the red to green scale (a*), the blue to yellow scale (b*), and the lightness extreme (L*). In a preliminary experiment, significant differences were observed in the surface color of visually identical white tablets from four different products. These differences were found to be product and not batch specific. The utility of colorimetry in identifying imitator products was then demonstrated by comparing the color signatures of the innovator Viagra® tablets to imitator Sildenafil tablets, which were procured from nine different online suppliers. While it is not a fool proof technique, data in this study demonstrates that colorimetry could be used as a simple inexpensive technique to identify innovative products and potentially alleviate the pandemic of counterfeit medicines, especially in areas around the world where counterfeiting is prevalent while sophisticated tools for their detection are not readily available.