Many of the legal alternatives to mephedrone available on the internet contain the same substance or related chemicals and are just as risky, experts warn today.
Mephedrone was widely sold as a "legal high" until it was banned in April following the deaths of two teenagers. Louis Wainwright, 18, and Nicholas Smith, 19, died in March, sparking concern about the stimulant. Toxicology tests in May showed they had not taken the drug.
Mephedrone, also known as Meow Meow, Bubbles and M-Cat, is made up of a compound class called cathinones. It is now a Class B drug.
Today, experts from Liverpool John Moores University, the University of Liverpool and Lancaster University, say many drugs being sold as substitutes for mephedrone are also cathinones.
Writing in the British Medical Journal, they say that "one of the most prominently discussed second-generation products" is Energy 1 (also called NRG-1 or naphyrone).
"These products are offered as legal substitutes for the recently criminalised 'legal highs', the mephedrone derivatives," they write.
The researchers bought 17 drugs from 12 UK-based websites over a six-week period following mephedrone's ban.
They chemically analysed the drugs and found that most of the "NRG-type products were recently banned cathinones that just carried a new label".
They write: "This suggests that both consumers and online sellers are, most likely without knowledge, at risk of criminalisation and potential harm.
"This has important health and criminal justice consequences that will require carefully thought-out responses and further investigation."
Simon Brandt, a senior lecturer in analytical chemistry at John Moores, said: "The analysis showed that those sold as legal alternatives turned out to be related to mephedrone and some of them were just, in fact, mephedrone.
"About 70 per cent contained mephedrone or mephedrone-related products. When we analysed these white powders we found cathinones, related products or a mixture. Nobody knows what the health effects of these mixtures are, or what they could be."
The Advisory Council on the Misuse of Drugs is due to publish advice today on NRG-1. It is widely expected to recommend the drug is banned.