Analysis and detection of drugs and counterfeit medicines with hyperspectral cameras
Development, production and marketing of drugs involve significant amount of investments, and is therefore prone to the production of illegal or fake products. In addition of being illegal, counterfeit drugs may cause high health risks to a patient. More and more countries invest money in governmental agencies to track these illegal and counterfeit drugs. New technologies and methods are developed for this purpose, including hyperspectral imaging. The aim of this study is to assess the relevance of such system to support the detection of these fake and illegal products.
In this study, two types of samples were investigated: i) genuine and counterfeit tablets, containing sildenafil (i.e. Viagra®); and ii) tablets of MDMA (i.e. 3,4-methylenedioxy-methamphetamine, ecstasy), with different concentration. All samples were investigated with SPECIM hyperspectral imaging systems in order to measure their spectral reflectance. Drugs containing sildenafil were studied with Visible and Near-Infrared (VNIR; 400 – 1000 nm) and Short Waves Infrared (SWIR; 1000 – 2500 nm) hyperspectral cameras, whereas tablets made of MDMA were investigated with an extended Near Infrared camera (eNIR; 600 – 1600 nm).
Before analysis, raw images were pre-processed by subtracting dark current from the data, and then normalizing in respect to a white tile. It provided reflectance spectra for each pixel in the collected images, which were then analyzed with Principal Component Analysis (PCA) algorithms.
According to the results, both VNIR and SWIR cameras are suitable to separate fake tablets of Viagra® from genuine ones. Although the PCA highlights that tablets were most likely made of the same active principal ingredient (API; PC1 was not relevant to separate the tablets, but others), there were spectral differences within the vicinities of 850 – 1000 nm, 1550 and 2250 nm. The examined differences in spectral properties are due to variation in the chemical composition of original and counterfeit drugs (active pharmaceutical ingredient and excipients) and/or another internal structure resulting from a different production technology. Besides, the SWIR spectral camera underscored that fake tablets were not homogeneous, unlike the genuine ones.
The spectral region 600 – 1600 nm is appropriate to investigate tablets made of MDMA. Despites tablets had different colours (green and red) and the eNIR camera overlapped with the visible region of the spectrum, the spectral features between samples were identical. This highlights that tablets were made of the same ingredient (here as well, PC1 did not show either any difference between tablets). However, beyond 1100 nm, slight deviations within the spectral features are observed, and samples can be grouped according to their concentration of MDMA.
Based on the above, we can conclude that hyperspectral cameras show potential to investigate solid dosage forms of drugs. VNIR, SWIR and eNIR hyperspectral imaging can be successfully applied for content composition identification and quantification and for assessing components distribution/homogeneity of API and excipients. It also enables to distinguish between genuine and counterfeit drugs. Also, depending of the scrutinized substance, different spectral region would be suitable.