USP evaluates Raman device's potential to detect counterfeit and substandard medicines

With substandard and counterfeit medicines a dangerous and growing problem in the developing world and elsewhere, identifying new technologies to detect such drugs is an urgent matter. In a new study published in the Journal of Pharmaceutical and Biomedical Analysis, scientists from the U.S. Pharmacopeial Convention (USP) evaluated a handheld Raman device's potential to detect counterfeit and substandard medicines. The device, called TruScan-, is currently used to test Active Pharmaceutical Ingredients (API) and finished pharmaceutical products, and it was evaluated for its ability to differentiate among drug products with different APIs, different brands of the same API, and drug products having the same API but of different strengths, with focus on the specificity and precision of the testing. While TruScan could be used successfully in the initial screening for authentication of the identity of certain targeted medicines, it may not be reliable enough to establish whether the medicines are substandard or not. The print version of the study appears in the journal's February issue.

"Thin Layer Chromatography (TLC) test methods, such as Minilab-, which PQM uses on a regular basis to detect counterfeit and substandard medicines, have been in the market for several years. They are quite reliable, but require specific training and the use of chemicals," said Mustapha Hajjou, Ph.D., lead author of the study, and a program manager for USP's Promoting the Quality of Medicines program (PQM), which is funded by USAID. "There is an increased interest in other, 'non-invasive' spectroscopic methods to detect counterfeit medicines, including near-infrared (NIR) and Raman spectroscopy, like the device we tested, and those would undoubtedly be simpler to use. We just have to make sure they produce reliable results for various types of medicines including substandard medicines, and that is what we tried to evaluate with the TruScan device," he explained. USP is a scientific, nonprofit public health organization that sets standards for the quality of medicines, food ingredients and dietary supplements. USP standards are used in more than 140 countries.

Antimalarial medicines artesunate and combination sulfadoxine-pyrimethamine (SP) were used in the evaluation because of their common use and the prevalence of counterfeit and substandard products in markets where malaria is endemic, and because of previous unfavorable reports of testing these products with a Raman device. Ibuprofen and acetyl salicylic acid tablets were also used, due to their wide range of products with different strengths-allowing the scientists to study the device's ability to discriminate between these products. A reference spectrum or signature, reference standard or a formulation (whole tablet) was created first to be compared to the spectra of other samples. Samples testing yielded either a match or fail result.

Results for the evaluation of antimalarials showed that the device's precision depend on the nature and strength of the active pharmaceutical ingredient (API). All medicines tested obtained acceptable precision results although, for some products, the results were well below 100 percent. The low matching results were attributed to high fluorescence masking the Raman signal, which could generate false negative results in authenticating medicines.

In the specificity evaluation, the Raman device successfully differentiated APIs, which would be useful in testing counterfeit finished products containing the wrong API. However, in the comparison with different lots of the same product and the comparison with similar products from different manufacturers, some samples did not match themselves, and the SP samples from four different manufacturers matched the comparator, showing the device is not sufficient to discriminate among these samples.

The device was also evaluated for its ability to detect different strengths of the same API. Acetyl salicylic acid and acetaminophen tablets all matched the comparator product, regardless of the sample strength, showing the device's limitation in possibly detecting substandard medicines from these classes of drugs.

"We concluded that TruScan will likely detect counterfeit medicines that lack API or have the wrong API, but we cannot rely on it to detect substandard medicines. This is especially true in the case of fixed-dose combinations, where one API may have a strong Raman scatter, masking the signal for other APIs. Because most of the effective medicines treating malaria, HIV/AIDS, and tuberculosis are fixed-dose combinations, we need to be very cautious in using this device for assessment of substandard medicines, says Patrick Lukulay, Ph.D., vice president of USP's Global Health Impact Programs and program director for PQM.