Use of NIRS to detect counterfeit drugs

The introduction of counterfeit drugs since the 1990s into the pharmaceutical market is a big source of concern. Medicines such as Viagra, Cialis, Levitra are examples of these counterfeit products. What constitutes a drug is the Active Pharmaceutical Ingredient (API) and also the excipient products which defines its shape, colour and administration. Each medicine has its unique chemical and physical characteristics that can be verified using an analytical technique. The counterfeiter must not only get the API correct, but also needs to make an effort to get the physical characteristics right. Figure 1 shows a comparison of fake and authentic Viagra tablets.

Figure 1: Fake vs. Real Viagra tablets (Reference 1)

Regulatory agencies around the world have started to do screening for counterfeit medicines entering through the borders of each country. Using bulky and expensive analytical instruments in the field is not practical and for this reason, Near-IR spectrometers are finding useful applications for identifying counterfeit drugs. Near IR spectroscopy is a fast, non-destructive technique that requires no sample preparation and makes it possible to find the chemical and physical fingerprint of the drug. Handheld near-IR spectrometers are also very useful because the inspectors can take the instrument to local pharmacies and airports to scan the drugs and test their authenticity.

In one study (Reference 2), a portable near IR instrument working in the range 720-1090 nm was used to scan counterfeit drugs. The range of the instrument covered the third overtone region with a 10 nm wavelength interval. The third overtone region is shown among other overtones and combination band regions in Figure 2. The intensity of spectra decreases as the overtone number increases just like it works for any harmonic oscillator.

Figure 2: Absorption chart showing different overtone and combination band regions

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In this study (Reference 2) counterfeit products of Cialis and Levitra from several different batches were tested using the aforementioned portable spectrometer that operated in the transmission mode. The transmission spectra were converted to absorption spectra and second derivative and Standard Normal Variate (SNV) pre-processing were applied to the spectra. Principal Component Analysis models were built on the preprocessed spectra which could distinguish between the counterfeit and the authentic products.  Figure 3 shows the difference between the SNV applied authentic and counterfeit Levitra.

Figure 3: SNV applied spectra of Authentic and Counterfeit Levitra (Reference 2)

In another study (Reference 3), a lab-based FOSS NIR spectrometer with a spectral range of 1100-2500 nm and a 2 nm resolution was used to look at authentic and counterfeit samples of Viagra, and Anadin version of Ibuprofen. The latter contains 18 different excipients in addition to its ibuprofen API (Reference 3). The instrument worked in the diffuse reflection mode and after acquiring the diffuse reflection spectra from Plavix samples (medicine to reduce the risk of heart disease), they were converted into absorption spectra. Next the second derivative and SNV scatter correction preprocessing were applied to the spectra and a Principal Component Analysis (PCA) model was constructed. The samples came from 3 different batches. Figure 4 shows the score plot based on the PCA analysis.

Figure 4: Score plot identifies counterfeit and Authentic Plavix (reference 3)

The score plot clearly distinguishes between the counterfeit and authentic batches.

Allied Scientific Pro offers the Nirvascan Spectrometer which is a portable Near IR spectrometer operating in the second over region and has the range of 900-1700 nm. It communicates via blue-tooth with an app and provides the user with the reflection and absorption spectra from the solid/powder samples. Figure 5 shows the instrument measuring from Aspirin tablets and the obtained spectrum.

Figure 5: Diffuse reflectance measurement from Aspririn and Nirvascan instrument

The Nirvacloud platform offered by Allied Scientific Pro enables the user to upload the spectra to the cloud platform and build the necessary PCA models for sorting. The platform is free for those who purchase the instrument.

For more information regarding the Nirvascan instrument, refer to the following link:



2- Use of a portable near infrared spectrometer for the authentication of tablets and the detection of counterfeit versions, A.J. O’Neil et. Al, Journal of Near Infrared Spectroscopy, Proceedings of the 13th international conference on Near IR Spectroscopy, 2007.

3- The use of near infrared spectroscopy to detect counterfeit medicines, T.Moffat, Spectroscopy Europe world, Oct 2010.

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