Abstract
There is an ongoing need for new or alternate approaches to distinguish between innovative pharmaceutical products from counterfeit or visually similar medicines. In this study we hypothesized that the quantitative measurement of the color on the surface of tablets, using the CIE L∗a∗b∗ color space, might be used to accomplish this objective. Several proof-of-concept studies were carried out in which ColorQuest XE colorimeter was used to measure the tristimulus L∗, a∗, and b∗ color values from the surface of white and colored pharmaceutical tablets. Tristimulus values represent the red to green scale (a∗); the blue to yellow scale (b∗); and the lightness extreme (L∗). In a preliminary experiment, we demonstrated that each tablet from 54 products have a unique L∗a∗b∗ parameter within the 3D tristimulus color space. The utility of colorimetry in identifying imitator products was then demonstrated by comparing the color signatures of the innovator Viagra® tablets with imitator sildenafil tablets, which were procured from nine different online suppliers. While not an infallible technique, data in this study demonstrated that colorimetry might be used as a simple 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.
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