Research and analysis

Cover letter: review of the evidence on the use and harms of carisoprodol (accessible)

Published 6 November 2025

ACMD Chair: Prof Owen Bowden-Jones
NPS Committee Secretary: Yetunde Animashawun
1st Floor (NE), Peel Building
2 Marsham Street
London
SW1P 4DF

ACMD@homeoffice.gov.uk

Rt Hon Sarah Jones MP
Minister of State (Minister for Crime and Policing)
2 Marsham Street
London
SW1P 4DF

6 November 2025

Dear Minister,

Re: ACMD report – A review of the evidence on the use and harms of Carisoprodol

During the 68 th session of the United Nations Commission on Narcotic Drugs (CND), carisoprodol, a centrally acting muscle relaxant, was placed under Schedule IV of the 1971 Convention on Psychotropic Substances. As a signatory to the Convention, the United Kingdon was therefore obliged to consider and assess the appropriate legal control measures for this compound.

The ACMD is pleased to enclose its report which considers the use, harms and control of carisoprodol. The report includes recommendations on appropriate domestic controls under the Misuse of Drugs Act 1971 and Misuse of Drugs Regulations 2001, following a thorough review of the evidence available. The ACMD is grateful to national and international experts who provided their expertise to this review.

The following conclusions were reached after review by the ACMD Carisoprodol Working Group:

1. In the UK there are no legitimate uses of carisoprodol and meprobamate in human or veterinary medicine. There may however be visitors to the UK who have been prescribed carisoprodol in another country.

2. Acute administration of high doses of carisoprodol can produce hypomania, confusion, disorientation, agitation and partial amnesia. Very high doses may result in respiratory failure, coma and death. When carisoprodol is taken along with benzodiazepines and opioids the risk of overdose is higher as all three classes of drug depress respiration.

3. Prolonged use of carisoprodol induces addiction and dependence. In individuals who have been taking carisoprodol over a prolonged period cessation of drug use will likely precipitate a withdrawal response.

4. Data from UK drug checking (seizures and voluntarily submitted samples) indicate that carisoprodol is available on the illicit drug market either on its own or in combination with the opioid tapentadol.

5. Evidence for the involvement of carisoprodol in non-fatal and fatal overdoses in the UK, alone or in combination with other drugs, is incomplete due to insufficient routine forensic testing for carisoprodol and its metabolite meprobamate.

6. Accurate information on the involvement of carisoprodol in drug overdoses in the UK will only be available when routine testing for carisoprodol and its metabolite meprobamate is performed across the country.

7. Because of the recent increase in the numbers of detections of carisoprodol in the illicit drug supply in the UK and the likelihood of further increases in its prevalence as well as the potential health and social harms associated with its use, the ACMD advises that control of carisoprodol via the Misuse of Drugs Act 1971 is necessary. Harms are considered to be broadly equivalent to those of other sedatives such as benzodiazepines and zopiclone.

Based on the evidence available, the ACMD has made the following recommendations:

Recommendation 1:

Given the harms associated with its use carisoprodol should be added to Class C of the Misuse of Drugs Act 1971 and placed in Schedule 4 Part 1 of the Misuse of Drugs Regulations 2001 (as amended).

Leads: Home Office

Measure of outcome: The inclusion of the listed compounds in Class C of the Misuse of Drugs Act 1971, Schedule 4 of the Misuse of Drugs Regulations 2001.

Recommendation 2:

a) Toxicological testing for both carisoprodol and its metabolite meprobamate should be performed routinely in cases of non-fatal and fatal overdose. Non-comprehensive screening hinders our capacity to understand trends in drug deaths.

b) The presence or absence of either an opioid or a benzodiazepine should be recorded for all deaths involving carisoprodol and/or meprobamate.

Leads: Home Office, Coroners in England, Wales and Northern Ireland and Procurators Fiscal in Scotland.

Measure of outcome: All post-mortem toxicology to include carisoprodol and meprobamate analogues on the testing panel.

Recommendation 3:

Resources should be developed for health professionals and drug services on the danger of carisoprodol overdose, and increased risk when combined with benzodiazepines and opioids. These resources to include information on how overdoses that may involve carisoprodol alone or in combination with other drugs should be treated.

Leads: UK Health Security Agency (UKHSA), Office for Health Improvement and Disparities (OHID), Public Health Wales, Public Health Scotland, the Department of Health Northern Ireland, the Association of Directors of Public Health and National Poisons Information Service (NPIS).

Measure of outcome: Information available for health professionals, and drug services.

Recommendation 4:

Information on the harm of carisoprodol and the risks of overdose should be developed in formats suitable for people who are currently using carisoprodol, those who may use it in future, their family and friends; as well as for the general public.

Information for people who are currently using carisoprodol or who may use it should highlight risk of addiction, dependence and overdose, and the increased harms of combining with benzodiazepines and opioids. Information for the general public should be provided through updates to national drug information channels (FRANK, DAN 24/7, Know the Score)

Leads: UK Health Security Agency (UKHSA), Office for Health Improvement and Disparities (OHID), Public Health Wales, Public Health Scotland, the Department of Health Northern Ireland and the Association of Directors of Public Health.

Measure of outcome: Readily accessible information being available for people who use drugs, their families and friends, and the general public.

We would welcome the opportunity to discuss this report in due course.

Yours sincerely,

Professor Owen Bowden-Jones
Chair of the ACMD

Professor Graeme Henderson
Carisoprodol Working Group Chair