The deadly risk of so-called 'legal highs' and other designer drugs, such as the notorious 'meow meow', has been confirmed by a huge leap in their links to drug-related deaths in the UK.
One expert described experimentation with such drugs as 'dancing in a minefield'.
'Meow meow', officially known as mephedrone and now illegal, is just one of a group of drugs called Novel Psychoactive Substances (NPS), which also includes the amphetamine-like substances Benzo Fury and PMA, amongst others. According to data published in the National Programme on Substance Abuse Deaths (NPSAD) report, compiled by experts at St George's, University of London, NPS are now linked to more drug-related deaths than ever before.
The prevalence of these drugs in the post mortem toxicology tests submitted to the report has increased 800% in three years, from 12 in 2009 to 97 in 2012. The number of cases where NPS were identified as the cause of death rose by almost 600% during the same period - from 10 deaths in 2009 to 68 in 2012. In many cases traces of multiple NPS were found, suggesting that drug users are experimenting with combinations of these drugs, as well as alcohol in some cases.
These drugs have undergone little or no human testing so their health effects are virtually unknown.
Professor Fabrizio Schifano, acting director of NPSAD, said: "We have observed an increase in the number and range of these drugs in the post mortem toxicology results and in the cause of death of cases notified to us.
"These include amphetamine-type substances, dietary supplements, ketamine derivatives, among a host of others.
"The worrying trend is that these type of drugs are showing up more than ever before. Clearly this is a major public health concern and we must continue to monitor this worrying development.
"Those experimenting with such substances are effectively dancing in a minefield."
The report also indicates an increase in the proportion of deaths involving stimulants such as cocaine and ecstasy-type drugs, following a decline in 2009 and stabilisation in 2010.
In total, the number of drug-related deaths reported to the NPSAD during 2012 was 1,613.
Opiates/opioids such as heroin and morphine, alone or in combination with other drugs continued to account for the highest proportion (36%) of reported drug-related deaths in 2012, a 4% increase compared to 2011 - a reversal of the decline in such deaths observed in recent years.