Simply measuring the colour of pharmaceutical tablets could be enough to distinguish between genuine and counterfeit drugs, say US researchers.
Using Pfizer's erectile dysfunction Viagra (sildenafil) and several knock-off copies to test the technique, the scientists from the University of Louisiana demonstrated that using colorimetry to test tablets could be "a simple technique to identify innovative products and potentially alleviate the pandemic of counterfeit medicines."
Quantitative measurement of the colour on the surface of tablets with a HunterLab ColorQuest XE tristimulus colorimeter could be used as a unique product identifier, alongside other anti-counterfeit measures such as the placement of serialized codes on medicine packs, they write in the Journal of drug Delivery Science and Technology.
The surface colour of the genuine tablet can be recorded for each lot of tablets and used as a reference against which samples of visually similar shape and colour can be tested without specialised analytical testing tools.
The technique – which is already used in the food and pharma industries for quality assessments and other purposes - could meet a requirement for an alternative identification approach that is inexpensive and can be carried out without access to laboratory facilities.
That makes it particularly suitable for areas of the world where counterfeiting is prevalent but "sophisticated tools for their detection are not readily available."
The technique is clearly not fool-proof and can be affected by surface contamination, the homogeneity of the tablets, handling and the possibility that they may change colour over time.
It can also not be used to test tablets in packaging, so has less utility than more sophisticated techniques such as nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), near infrared (NIR), mass spectroscopy (MS), and Raman spectroscopy.
"Efforts could also be made to manufacture tablets with a unique colour combination that is difficult to emulate," suggest the authors.