Designer drugs have led to a surge in UK hospital admissions, an international drugs agency has warned, as a report revealed a dramatic rise in the number of websites selling so-called legal highs.
The UN study identified an "unprecedented" increase in the emergence of new mind-altering substances on the market from five per year between 2000 and 2005 to almost one a week in 2011.
Deaths or serious health consequences among users rose with these figures, it said, while the number of internet sites supplying the drugs to Europe increased by more than 300% in two years.
Around one fifth of these sites were hosted on servers based in Britain, the International Narcotics Control Board (INCB) said.
The INCB study said the abuse of illicit drugs in Europe has stabilised in recent years, albeit at a high level.
But the emergence of psychoactive substances - so-called designer drugs or legal highs - posed a "major challenge", it said.
"In the United Kingdom, there were increases in hospital admissions and medical appointments owing to new psychoactive substances, as well as reports of health problems caused by the regular use of such substances," the report stated.
While overall drug-related deaths in Britain fell by 14% from 2009 to 2010, fatalities caused by the abuse of new substances increased significantly, from six cases in 2008 to 44 cases in 2009, the study found.
It said: "In recent years, there has been an unprecedented increase in the emergence of new psychoactive substances not within the purview of the international drug control conventions."
It added: "The number of Internet-based retail sites selling psychoactive products and shipping to European Union member States increased from 170 in January 2010 to 314 in January 2011 and 690 in January 2012.
"About a third of them were hosted on servers based in the United States, and a fifth of them were hosted on servers based in the United Kingdom."
Citing figures from the European Monitoring Centre for Drugs and Drug Addiction, it said the number of notifications relating to new psychoactive substances hit 49 in 2011, meaning a new drug appeared on the market almost every week.
It said: "Although it is impossible to know the exact number of new psychoactive substances on the market, experts have advanced estimates running well into the thousands.
"As abuse of these substances has increased, so too has the number of users who have experienced grave health consequences or even suffered death due to exposure to them.
"In many countries, use of such substances has manifested itself in marked increases in emergency room visits for adverse health reactions caused by the ingestion of new psychoactive substances, as well as in significant increases in calls to poison treatment centres."
The study found "mounting evidence" to suggest many new drugs were being manufactured in China and India.
It concluded: "A particular challenge to Government efforts to place new psychoactive substances under national control is the difficulty of identifying those substances in a timely manner, given the rapid succession of new substances entering the market, their inconsistent chemical composition and the lack of technical and pharmacological data and reference material, as well as insufficient forensic and toxicological capacity on the part of some states."
THE REPORT'S FINDINGS
- Mephedrone - which was banned and made a class B drug in 2010 - was the third most popular drug among those aged 16 to 59.
- Abuse of the club drug, also known as Meow Meow, Bubbles and M-Cat, was at 1.4% in England and Wales in the period 2010/11;
- The UK is the only major European country allowing the import of khat, a substance widely consumed in East Africa and parts of the Middle East for its stimulating effects;
- The abuse of antidepressants has increased in Northern Ireland;
- The number of foreign nationals being used as couriers to smuggle drugs into the UK, Canada and the US has risen.