The counterfeiting of pharmaceuticals is a global issue that is expanding each year. The severity of drugs counterfeited has increased from lifestyle drugs to include lifesaving (such as anticancer) types in recent times. The miniaturization of instrumentation has led to out-of-laboratory analysis for product authentication. Raman spectroscopy is ideal for pharmaceutical identifications and has been proven to detect counterfeit drugs. Portable instruments are available with dispersive technology and laser excitation at 785 nm for remote analysis. This study compares a modern portable Raman instrument equipped with a 1064-nm laser with one using a 785-nm laser. It is shown that authentic tablets are distinguished from the counterfeit tablets nondestructively, without the need to remove tablet coating.
Counterfeit medications are a problem globally, both in developing countries and developed nations. It is estimated that more than 10% of the global market is made up of counterfeits, with that number varying widely based on geographic region. Recently, there have been more reports of counterfeit lifesaving (for example, anticancer) types of drugs, not just the lifestyle drugs that made up much of the counterfeit market in the past (1,2). Fast, easy, and reliable methods to identify counterfeit drugs are crucial to reducing this problem. Raman spectroscopy is sensitive to molecular vibrations and as such is highly specific to the material that is measured. This makes Raman spectroscopy ideal for pharmaceutical identifications, and it has been proven to detect counterfeit drugs (3–6). The development of miniaturized portable Raman instruments in recent years has led to out-of-laboratory analysis for product authentication, which makes counterfeit identification practical at many different points in the supply chain and allows for faster detection and shut down of counterfeiting operations.
This study compares Raman spectra measured from two different portable Raman spectrometers: one with the more traditionally used 785-nm excitation and the other with the more recently developed 1064-nm excitation. It looks at the specificity of the Raman spectra from the different excitation wavelengths as well as the ability to measure nondestructively through tablet coatings and original medication packaging with no sample preparation.Experimental
Samples were analyzed with two different instruments. Measurements obtained with 1064-nm laser excitation were done using a Rigaku Xantus-2 portable Raman instrument equipped with a cooled InGaAs detector. Measurements with the 785-nm laser excitation were performed using a portable Raman instrument equipped with a charge-coupled device (CCD) detector. For both instruments, a laser power of 300 mW was used.
Samples were measured in a variety of physical shapes: capsules, powders, tablets, and original vials containing powders. Samples that were capsules or powders were transferred to borosilicate vials and measured through glass vials using each instrument's specific vial holder. Tablets and powders in original vials were measured as is with each instrument's on-board point-and-shoot tip. Samples of authentic and counterfeit products used were: Alli (orlistat), Viagra (sildenafil citrate), and Duphaston (dydrogesterone). Authentic products were purchased from bona-fide pharmacies; counterfeits originated in Asia.
Raman data were reviewed post calibration from 300 to 1800 cm-1 using Thermo Omnic software (version 8.2), or with Igor Pro software (version 6.22A).