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novel ‘legal highs’ in the UK

Download ‘Science Media Centre Fact Sheet – Legal highs‘ as pdf.


Various compounds are sold as legal highs in the UK, often through internet sites though also in some shops. ‘Legal highs’ as a term can be used to describe everything from alcohol and nicotine, through to herbal mixtures and compounds synthesised in the lab.

This factsheet will focus only on novel laboratory-made compounds which have recently made their way into the UK market, often referred to as ‘designer drugs’. The compounds focussed on are:

Synthetic cathinones (e.g mephedrone, ‘bath salts’)
6-APB (Benzo Fury)
Synthetic cannabinoids (e.g. Spice, K2)


Many legal highs quickly become controlled (see sources/further information for a report on regulation), and the above drugs have a varying state of legality. The sale of substances is controlled in the UK through two acts of Parliament:

  1. The Misuse of Drugs Act 1971, through which ‘temporary class drug orders’ can be imposed before classifying substances as class A, B or C
  2. The Medicines Act 1968, which prohibits the sale of compounds for human consumption, hence products are sold as ‘research chemicals’ or similar

Prevalence and availability

  • Between 1997 and 2010, more than 150 new psychoactive substances were identified by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA)
  • The rate at which new substances appear on the market has increased, with record numbers of new substances being reported – 24 in 2009, 41 in 2010, and 49 in 2011
  • Most of the 41 new psychoactive substances identified in 2010 were synthetic cathinones or synthetic cannabinoids (see below for chemical classes)

Types of drugs & classes of compounds

Psychoactive drugs are often described using three broad categories based on their effects: Stimulants, depressants and hallucinogens. Like most drugs, legal highs fall into one or more of these categories:

Synthetic cathinones


Synthetic cannabis

Drugs are also often described by the class of chemicals which they belong to, and these are often tied to their psychoactive properties as above. Three commonly referred to classes are phenethylamines, tryptamines and cannabinoids.

There are examples of both illegal drugs and legal highs which fall into each of these classes:

Phenethylamines Tryptamines Cannabinoids
Illegal drug MDMA (ecstasy) Psilocybin (in magic mushrooms) THC (in cannabis)
Legal high Synthetic cathinones AMT Synthetic cannabis

Recent novel legal highs

Synthetic cathinones (‘bath salts’)

  • Compounds sold as ‘bath salts’ or ‘plant food’ are typically powders and come under various trade names including Ivory Wave, Ivory Coast, Purple Wave, Vanilla Sky and Cloud 9
  • These products usually contain a synthetic cathinone, and are based on phenethylamines, with stimulant and some hallucinogenic effects
    • Cathinone is an organic compound found in the khat plant – used traditionally as a stimulant in middle eastern countries
    • Cathinone is structurally very similar to amphetamine
  • There are a large number of synthetic cathinones, including:
    • Mephedrone
    • Naphyrone
    • Desoxypipradrol
    • MDPV
  • Mephedrone and many similar synthetic derivatives were made class B illegal drugs in the UK in April 2010, though there are similar compounds that fall outside of this legislation

Benzo Fury: 6-APB and 5-APB

  • Products labelled as Benzo Fury, usually containing the compounds 6-APB or 5-APB, are sold in powder or pellet form
  • 6-APB or 5-APB are of the phenethylamine class and have amphetamine-like properties
  • Chemically 6-APB and 5-APB are similar to MDA, with a benzofuran ring replacing a similar chemical structure in MDA
    • MDA is closely related to MDMA, the compound most commonly referred to as ecstasy
  • Compounds other than 6-APB or 5-APB can wholly or partially make up products sold as Benzo Fury, including:
    • D2PM (illegal)
    • Benzophenone (legal)
    • TFMPP (illegal)
    • Caffeine (legal)
    • BZP (illegal)
  • 6-APB and 5-APB are currently legal in the UK


  • Methoxetamine, MXE or Mexxy is sold as a powder and is a near chemical analogue of the illegal drugs ketamine and PCP
  • It has a hallucinogenic and depressant effect
  • It is billed as a ‘bladder friendly’ alternative to ketamine though these claims are as yet unsubstantiated
    • Chronic use of ketamine can cause severe bladder damage
  • Methoxetamine is currently subject to a temporary class drug order in the UK


  • MDAI is an amphetamine-like phenethylamine, which became popular after the banning of mephedrone
  • Along with some other similar compounds compounds, MDAI was originally developed for research into the effects of MDMA
  • The chemical structure is directly derived from MDA, but it has distinct pharmacological properties
  • MDAI and similar compounds are currently legal in the UK

Spice and K2: synthetic cannabinoids

  • Products sold as Spice or K2 consist of packets of herbs and claim to have a similar effect to that of cannabis
  • In addition to the herbs listed on the packaging, the products contained small amounts of synthetic cannabinoids – compounds that mimic the effect of THC, the active ingredient in cannabis
  • There are various groups of compounds that mimic THC, often with a much higher potency, making the small quantities added difficult to detect
  • 5 distinct chemical classes of synthetic cannabinoids were classified as a class B drug in the UK in 2009, though other compounds have appeared since then that fall outside the legislation


  • AMT is an LSD-like hallucinogenic drug, of the tryptamine class
  • AMT and similar tryptamines currently lie outside of UK legislation

Sources / further information

ACMD report into legal highs (2011) – see Annexes for drug related deaths and specific pharmacologies

ACMD reports

EMCDDA Annual Report 2011 – New drugs and emerging trends

Detailed information on compound classes of legal highs

Drugwise page on legal highs

Temporary class drug order factsheet

Independent Scientific Committee on Drugs 

This is a Factsheet issued by the Science Media Centre to provide background information on science topics relevant to breaking news stories. This is not intended as the ‘last word’ on a subject, but rather a summary of the basics and a pointer towards sources of more detailed information. These can be read as supplements to our Roundups and/or briefings.

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