Scientists develop test to probe fake Erimin 5 market

Scientists have developed a quick analytical test for an anxiety and sleeping medicine that is widely counterfeited in several Asian countries.

Police Malaysia, Singapore, Indonesia and Hong Kong have been encountering fake versions of Sumitomo's Erimin (nimetazepam), a short-acting benzodiazepine that was discontinued by the Japanese drugmaker last year after more than 20 years on the market.

Erimin has never been approved in Malaysia but is commonly used there as a recreational drug - with the majority of tablets found in the market believed to be counterfeit. The drug - sometimes referred to as 'Happy-5' - is popular with heroin users as it can extend the high from the opioid whilst reducing withdrawal symptoms.

While the fakes used to contain nimetazepam and certain other benzodiazepines, more recently they are made with phenazepam, a long-acting benzodiazepine drug developed in the former Soviet Union in the 1970s. The substitution is thought to have been introduced to stay one step ahead of enforcement agency analytical teams.

Scientists at the Illicit Drugs Laboratory of Singapore have adapted an ultra-high-pressure liquid chromatography (UHPLC) with ultraviolet (UV) detection method - already being used to detect nimetazepam - so it can be used to quickly detect phenazepam.

"In 2012, following the notification by our Malaysian counterpart forensic laboratory of a very large seizure of Erimin 5 containing phenazepam, this laboratory started to encounter several seizures of Erimin 5 tablets containing only phenazepam," write the researchers in the journal Drug Testing and Analysis.

Tablets from five different seizures submitted to the laboratory in 2013 were found to have a dosage of about 2.4 milligrams, and the test had an uncertainty of around 3 per cent.

The team also used thin-layer chromatography (TLC) to examine dyes in tablets from several seizures in order to differentiate between different counterfeit samples, and suggests the methods could be used for surveillance studies to provide intelligence of the counterfeit trade.