Cat-and-mouse chase: Test measures in-fashion phenazepam counterfeits

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  • Published: Sep 14, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: HPLC
thumbnail image: Cat-and-mouse chase: Test measures in-fashion phenazepam counterfeits

Erimin 5

Governments and covert chemists have long been in a perpetual game of cat and mouse. As pharma unlocks the molecular shapes that treat seemingly untreatable problems, backstreet chemists take these blueprints and cook up their own in unlicensed laboratories.

Governments and covert chemists have long been in a perpetual game of cat and mouse. As pharma unlocks the molecular shapes that treat seemingly untreatable problems, backstreet chemists take these blueprints and cook up their own in unlicensed laboratories, with their eyes on the street value of these counterfeit drugs.

When authorities eventually crack down on one type, by devising the necessary analytical methods, underground chemists are already one-step ahead and have the next season’s drug under mass production. In years gone by, nimetazepine was a popular drug, but a series of crack-of-dawn swoops by Malaysian authorities resulted in the seizure of over four million counterfeit tablets masquerading as genuine Erimin®. Strangely, though, these ‘Erimin 5’ pills, as law enforcement calls these bogus tablets, contain phenazepam and not a trace of nimetazepine. The cat-and-mouse-race has begun once more.

Phenazepam is a benzodiazepine in high demand in some parts of south-east Asia. First concocted by Soviet scientists in the 1970s, the anti-anxiety and all-around relaxant was never approved outside of the iron curtain, but that has not stopped its illicit use in prolonging the highs and reducing the lows associated with heroin abuse, proving particularly troublesome to in Indonesia, Hong Kong, Malaysia, and Singapore.


Concerned for public health and safety, forensic scientists at the Illicit Drugs Laboratory of Singapore set out to aid law enforcement authorities by providing them with the tools required to classify batches based on their dosages of benzodiazepines. Their simple test could also form the basis of a surveillance study documenting all seized counterfeits.

Adapting their UHPLC-UV assay developed 12 years previous to determine the then-fashionable nimetazepam, Lim and colleagues tuned their UV diode to a wavelength of 230 nm to detect phenazepam. Prior to this, phenazepam was separated from its related benzodiazepams over a simple 5-minute isocratic mobile phase containing trace concentrations of potassium phosphate salts.

Quantitation was made against a seven-standard curve, which maintained linearity from 20 to 240 ng/mL, paving the way towards ‘a single-point calibration’ for routine analyses. In the absence of certified reference samples, Lim took a batch of ‘blank’ Erimin pills with standardised levels of menthol, lactose, palmitic and stearic acids across them and spiked these with phenazepam at appropriate levels to mimic the real counterfeit samples. Recovery was achieved with 98.5% accuracy.

Excipients and dyes

Previous seizures have shown that pill batches vary in many areas—their profiles of benzodiazepames, for example, and even their use diluent and dyes could help forensics. Accordingly, the authors also devised numerous assays that would give forensics the tools to build up a comprehensive profile of a pill’s ingredients.

Lim et al. developed a GC-MS assay that would mass analyse numerous benzodiazepames and potential additives, which were then identified by looking for concordance with spectral libraries. Furthermore, they also used infrared spectroscopy and thin-layer chromatography to detect tablet excipients and dyes.

Whilst counterfeits of bygone years used many dyes at once—including sunset yellow FCF, tartrazine, ponceau 4R, and erythrosine—to tinge their nimetazepam pills yellow, TLC separation of the recently seized drugs suggests that today’s rogue synthetic chemists now favour just quinoline yellow. What’s more, IR spectroscopy can also shed light on their production. Whilst, for example, nimetazepam tended to use lactose or mannitol as a diluent, the new generation phenazepam solely contains lactose.

In the War on Drugs, authorities have caught up with the runaway mouse—for the time being at least.

Related Links

Drug Testing and Analysis, 2016, Early View paper. Wendy et al.. Detection of phenazepam in illicitly manufactured Erimin 5 tablets.

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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