New psychoactive substances

Designer drugs, legal highs, NPS, novel psychoactive substances, research chemicals

What are New Psychoactive Substances?


New Psychoactive Substances

New psychoactive substances (NPS) are drugs which were designed to replicate the effects of illegal substances like cannabis, cocaine and ecstasy whilst remaining legal – hence their previous name ‘legal highs’.

NPS began to appear in the UK drug scene around 2008/09. They fall into four main categories:

Synthetic cannabinoidsthese drugs mimic cannabis and are traded under such names as Clockwork Orange, Black Mamba, Spice and Exodus Damnation. They bear no relation to the cannabis plant except that the chemicals which are blended into the base plant matter act on the brain in a similar way to cannabis.

Stimulant-type drugsthese drugs mimic substances such as amphetamine, cocaine and ecstasy and include BZP, mephedrone, MPDV, NRG-1, Benzo Fury, MDAI, ethylphenidate.

‘Downer’/tranquiliser-type drugsthese drugs mimic tranquiliser or anti-anxiety drugs, in particular from the benzodiazepine family and include Etizolam, Pyrazolam and Flubromazepam.

Hallucinogenic drugsthese drugs mimic substances like LSD and include 25i-NBOMe, Bromo-Dragonfly and the more ketamine-like methoxetamine.

NPS are sold online and in shops (although they were banned in 2016). The drugs come in brightly coloured packaging under a variety of brand names. The packaging may describe a list of ingredients but it’s impossible to be sure what’s inside and the contents of one branded package could change from week to week.


The effects of NPS vary significantly from drug to drug and, compared to more traditional drugs, we have relatively little information on them. However, there is a growing body of evidence to demonstrate the potential short and long-term harms associated with their use. There have been hospitalisations and deaths linked to NPS.

Reported harms during intoxication and come down include:

  • Overdose and temporary psychotic states and unpredictable behaviours;
  • Attendance at A&E and some hospital admissions;
  • Sudden increase in body temperature, heart rate, coma and risk to internal organs (PMA);
  • Hallucination and vomiting;
  • Confusion leading to aggression and violence;
  • Intense comedown that can cause users to feel suicidal.

Use was also associated with longer term health issues:

  • Increase in mental health issues including psychosis, paranoia, anxiety, ‘psychiatric complications’;
  • Depression;
  • Physical and psychological dependency happening quite rapidly after a relatively short intense period of use (weeks).

In the ONS report Deaths related to drug poisoning in England and Wales: 2019 registrations it states that there were 125 deaths involving new psychoactive substances in 2019 with synthetic cannabinoids being the most frequently mentioned NPS, contributing to 56 deaths.

Xylazine, a drug found in North America as a heroin/fentanyl adulterant recently had its first associated death reported in the UK. The drug is a veterinary medicine with sedative, analgesic and muscle relaxant properties.

The law

While many of these drugs were once legal, with the advent of the Psychoactive Substances Act it is now illegal to produce, supply, or import them for human consumption – including for personal use. Possession for personal use is not an offence, unless in prison.

The Psychoactive Substances Act received Royal Assent on 28 January 2016 and came into force on 26 May 2016.

The act:

  • makes it an offence to produce, supply, offer to supply, possess with intent to supply, possess on custodial premises, import or export psychoactive substances; that is, any substance intended for human consumption that is capable of producing a psychoactive effect. The maximum sentence will be 7 years’ imprisonment
  • excludes legitimate substances, such as food, alcohol, tobacco, nicotine, caffeine and medical products from the scope of the offence, as well as ‘poppers’ and controlled drugs, which continue to be regulated by the Misuse of Drugs Act 1971
  • exempts healthcare activities and approved scientific research from the offences under the act on the basis that persons engaged in such activities have a legitimate need to use psychoactive substances in their work
  • includes provision for civil sanctions – prohibition notices, premises notices, prohibition orders and premises orders (breach of the 2 orders will be a criminal offence) – to enable the police and local authorities to adopt a graded response to the supply of psychoactive substances in appropriate cases
  • provides powers to stop and search persons, vehicles and vessels, enter and search premises in accordance with a warrant, and to seize and destroy psychoactive substances

In November 2018 the Home Office published a review of the Act that sought to measure changes in outcomes before and after its implementation and thereby provide an indication of whether its aims are being achieved. The review concluded that

  • The open sale of NPS were largely eliminated
  • there was a significant fall in NPS use in the general population 
  • there was a reduction in health-related harms (likely to have been achieved through reduced usage)

However there was still concern over the supply of NPS by street dealers, the continued development of new substances, the potential displacement from NPS to other harmful substances, and continued high levels of synthetic cannabinoid use among the homeless and prison populations. A study published in 2021 reviewed the effects of the Act and concluded that the number of deaths following NPS use has risen despite introduction of the Act.

Some synthetic cannabinoids like Spice are controlled as Class B substances under the Misuse of Drugs Act. Offences for Class B drugs are:

  • Possession – Maximum sentence – 5 years/fine/both
  • Possession With Intent To Supply – Maximum sentence – 14 years/fine/both
  • Supply (including being concerned in supply, conspiracy to supply, aggravated supply and offer to supply) – Maximum sentence – 14 years/fine/both
  • Production – Maximum sentence –  14 years/fine/both

However, maximum sentences are rarely used. See this page from Release for more detailed information on sentencing.


According to a report from the Office of National Statistics, Drug misuse in England and Wales: year ending June 2022, the level of NPS use in the last year among adults aged 16 to 59 years was 0.4% and 0.9% for those aged 16 to 24 years. This showed no change compared with the previous report, for the year ending March 2020.

See also DrugWise’s printable factsheet on NPS (PDF)

Related links

Review of the Psychoactive Substances Act 2016, 2018

Spice (Synthetic Cannabinoids) Briefing for professionals 2017 (PDF)

Psychoactive Substances Bill: evaluation review, 2017
An evaluation review of the Psychoactive Substances Bill by the Advisory Council on the Misuse of Drugs (ACMD) | ACMD, UK

New psychoactive substances in Europe: legislation and prosecution — current challenges and solutions, 2016
The European new psychoactive substances (NPS) market has increased at a speed that established drug control laws struggle to match. Various countries have therefore introduced new legal responses to this phenomenon, based either on existing laws that focused on consumer or health protection or medicinal products, or by developing innovative new legislation. In 2014, the Court of Justice of the European Union ruled that substances are not medicinal products if they do not have beneficial effects on human health, thus restricting the use of such laws for NPS control | EMCDDA/Eurojust, Portugal

NPS Come of Age: A UK Overview, 2016, (PDF)
This report, written by Harry Shapiro is a 2016 DrugWise publication based on work first published by DrugScope in 2014 and 2015. It covers the history of New Psychoactive Substances (NPS); the effects and characteristics of the drugs themselves; the prevalence of their use; treatment and education interventions; and the legislative responses; including, of course, the Psychoactive Substances Act. There are also links to many further sources of information | DrugWise, UK

Circular 004/2016: Psychoactive Substances Act 2016
Provides information about the Psychoactive Substances Act, which comes into effect on Thursday 26 May 2016 | Home Office, UK

Psychoactive Substances Act 2016: guidance for researchers, 2016
This guidance is to help researchers comply with the Psychoactive Substances Act, which comes into effect on 26 May 2016 | Home Office, UK

Psychoactive Substances Act: guidance for retailers, 2016
This guidance is to help retailers understand the Psychoactive Substances Act 2016, which comes into effect on 26 May 2016 | Home Office, UK

NPS Communications toolkit, 2016 (PDF)
This pack outlines possible communication activity on the ban of New Psychoactive Substances (NPS) to carry out in your local area. It has been written for enforcement partners | Home Office / NPCC, UK

Business As Usual: A status report on new psychoactive substances (NPS) and ‘club drugs’ in the UK, 2015 (PDF)

Not for human consumption: An updated and amended status report on new psychoactive substances (NPS) and ‘club drugs’ in the UK, 2015 (PDF)

New Psychoactive Substances (NPS) resource pack, PHE, 2015

DrugWatch synthetic cannabinoid factsheet (Note this factsheet is from 2013) (PDF)
DrugWatch are an informal online professional information network established by a group of professionals working in the UK and Irish drugs sector and including DrugWise.

Updated July 2023