What are synthetic drugs?

New synthetic drugs, sometimes called new psychoactive substances or ‘designer drugs’, are increasingly found in the UK illegal drug market. These substances can be produced and used on their own, but are also often mixed with other drugs, like heroin, increasing the risk of overdose.

In 2024, researchers from the University of Bath reported that the synthetic cannabinoid drug ‘spice’ had been found in one in six vapes confiscated in schools in England.

What synthetic drugs are present in the UK?

Synthetic drugs available in the UK include:

• synthetic opioids like fentanyls and nitazenes, which mimic the effects of natural opioids, like opium or heroin, but can be up to 500 times stronger
• synthetic cannabinoids, which mimic the effects of cannabis
• synthetic cathinones, which mimic the effects of the plant khat

There is also concern about the appearance of new types of benzodiazepines, which have similar effects to drugs like diazepam (commonly known by its brand name Valium) and temazepam (a type of sleeping pill).

How harmful are new synthetic drugs?

Synthetic drugs carry health risks. Reports from the Advisory Council on the Misuse of Drugs (ACMD), which advises the government on harmful drugs, identify that:

• synthetic opioids carry risks of breathing problems and overdose
• synthetic cannabinoids can cause confusion, heart problems and psychiatric problems, including psychosis
• synthetic cathinones can cause stroke or heart attack and affect the liver and kidneys

The ACMD reports also identify potential social harms. For example, its report on synthetic cannabinoids found increased risks of education and employment problems, homelessness, antisocial behaviour, and road traffic accidents.

Deaths caused by new synthetic drugs

There is no single, definitive source of data on deaths caused by new synthetic drugs. However, the Office for National Statistics (ONS) publishes statistics on drug poisoning and drug misuse deaths in England and Wales based on the information recorded on death certificates, which may record the substances involved in poisoning.

Data for 2023 shows that, out of a total of 5,448 drug poisoning deaths, there were 170 deaths where a new psychoactive substance was mentioned on the death certificate. However, the ONS warns that this figure is an underestimate, as this information is not recorded for many deaths, and over half of all drug-related deaths involve more than one drug.

Differences in how deaths are recorded means that data for Scotland and Northern Ireland is not directly comparable with data for England and Wales. The latest available data from Scotland shows that new psychoactive substances were involved in 550 drug misuse deaths in 2023. In Northern Ireland, new psychoactive substances were mentioned on 14 death certificates in 2023.

In October 2024, the Office for Health Improvement and Disparities (OHID) published estimates of the numbers of deaths associated with synthetic opioids. Using data from laboratory tests in England, OHID estimated that there were 179 deaths involving synthetic opioids called nitazenes between 1 June 2023 and 31 May 2024. Researchers from Imperial College have reported that they detected nitazenes in 95 additional postmortems between 1 January and mid-October 2024.

How are synthetic drugs controlled?

In the UK, illegal drugs are controlled under the Misuse of Drugs Act 1971. Under the act, substances are categorised as Class A, Class B or Class C drugs, according to their potential to cause harm. Class A drugs are considered the most harmful and are subject to the strictest controls and most severe penalties for producing, importing, supplying or possessing them.

Generic controls for new synthetic drugs

Most controlled drugs are listed individually in schedule 2 of the Misuse of Drugs Act 1971, using their chemical name. Some groups of similar substances are controlled using a generic definition of their chemical structure. Schedule 2 includes generic definitions of several groups of drugs, including anabolic steroids, barbiturates, cannabinols, cathinones, fentanyls, and phenethylamines. The definitions are based on the core molecular structure of these substances.

In May 2024, the government introduced a generic control on nitazenes, based on a definition of their chemical properties. This means that new nitazenes can be controlled without individual substances having to be specifically named in schedule 2 of the Misuse of Drugs Act, which the government says will prevent drug gangs from adjusting drug recipes to bypass UK drug law.

The ACMD has recommended changes to generic definitions to include new versions of synthetic drugs. Most recently:

• In May 2025, the ACMD recommended that the current generic definition of cannabinoids should be updated to capture new semi-synthetic cannabinoids (SSCs) that can be found in vapes and sweets.
• In February 2025, the ACMD recommended that the current generic definition of cathinones should be updated to capture some new forms of these drugs that have the potential to cause health or social harms.

Other psychoactive substances

Under the Psychoactive Substances Act 2016, it is illegal to produce, supply, import or export any substance with a psychoactive effect. It is illegal to possess psychoactive substances in a custodial setting (such as a prison). However, it is not illegal to possess a psychoactive substance outside a custodial institution, unless it is with intent to supply.

This legislation was introduced to address the emergence of new synthetic drugs and other substances that were not controlled by the Misuse of Drugs Act, which were increasingly being sold as “legal highs” in the UK.

Reducing the harm caused by synthetic drugs

The government says the Home Office, Department of Health and Social Care, National Crime Agency, Border Force and National Police Chiefs Council are working with local partners to address the threat of synthetic drugs.

OHID has published guidance for local areas to help them to plan for incidents involving synthetic opioids, like nitazenes. The guidance urges local areas to plan and prepare for increasing harm from these drugs. It includes advice on collecting information about local trends in synthetic opioid use and harm, and communicating the risk to local services and people who use drugs.

Take-home naloxone

OHID guidance also recommends that local councils and drug treatment services should provide take-home naloxone.

Naloxone is an emergency antidote for opioid overdose. In December 2024, new regulations took effect to allow naloxone to be supplied on a ‘take home’ basis for use in a future emergency. Naloxone can now be supplied by drug treatment workers, healthcare professionals and the police, prison and probation services. The government has published guidance on supplying take home naloxone without a prescription.

Further reading

Commons Library, Misuse of drugs: regulation and enforcement

Commons Library, Debate on prevention of drugs deaths (26 March 2025)

Commons Library, Controlled Drugs (Procedure for Specification) Bill

Talk to Frank: Honest information about drugs

About the author: Claire Duddy is a medical and health specialist at the House of Commons Library.

Photo by: Анастасия Гайкова via Adobe Stock