Independent report

Covering letter to Dame Diana Johnson, Minister for Policing, Fire and Crime Prevention (accessible)

Updated 23 May 2025

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

Rt Hon Dame Diana Johnson DBE MP
Minister of State (Minister for Policing, Fire and Crime Prevention)
2 Marsham Street
London
SW1P 4DF

22 May 2025

Dear Minister,

Re: ACMD report – ‘Semi-synthetic’ Cannabinoids: Cannabinoids related to tetrahydro-cannabinol and cannabidiol

In recent years there have been increasing detections of hexahydrocannabinol (HHC), a semi-synthetic cannabinoid (SSC) in products such as vapes, sweets and e-liquid cartridges in Europe and the UK.

The ACMD is pleased to enclose the attached report describing the use and harms of HHC and other related semi-synthetic cannabinoids (SSCs), with the aims of identifying specific compounds causing health and social harms that are not captured by the current generic definition for cannabinoids

Most SSCs are produced through the process of manipulating the structure of the naturally occurring compound cannabidiol (CBD) and have similar psychoactive properties to tetrahydrocannabinol (THC), the principle psychoactive constituent of cannabis. Tetrahydrocannabinol acid (THCA), a naturally occurring compound (phytocannabinoid) found in the cannabis plant, is also included in this review due its structural similarity to THC and its recent detection in seizures of crystals and in vape canisters in the UK. It is converted easily to psychoactive Δ9-THC by application of heat, such as by smoking or vaping.

The report includes recommendations on classification and scheduling following a thorough review of the evidence available. The ACMD is grateful to national and international experts who provided their expertise to this review.

Based on the evidence obtained and reviewed on the uses and harms associated with these compounds, the ACMD has recommended that they should be controlled under the Misuse of Drugs Act 1971 (MDA) under Class B and placed in Schedule I of the Misuse of Drugs Regulations 2001 (MDR). The ACMD also recommends that the UK generic text for cannabinoids in the MDA should be updated so that psychoactive SSCs will be captured and controlled under legislation.

The ACMD have drawn the following conclusions, options for control and recommendations from the evidence presented in this report:

1.1. Several SSCs have been detected in drug markets internationally since 2019. Many of these are also available for purchase in a variety of forms in the UK, including sweets and vapes, and some have been detected in UK drug seizures. The possibilities that the data provided for this report underestimates the prevalence of these compounds in the UK or that other examples are in circulation in the UK cannot be excluded with confidence, especially due to limitations in sample testing for emerging NPS.

1.2. Many of the SSCs detected internationally are already controlled as Class B compounds under the MDA via the current UK generic text, including THC homologues (compounds with shorter or longer chain lengths) and their esters and ethers. The hexahydro derivatives of cannabinol, derivatives of cannabidiol (CBD), 11-OH compounds and THCA are not currently captured, although psychoactive examples are subject to the provisions of the PSA. Several of these uncontrolled substances have been reported in the UK, specifically HHC, HHCO, HHCP and THCA; of these, HHC has been detected most often.

1.3. There is accumulating evidence of the similarity in pharmacology as well as chemistry of many of these uncontrolled examples to Δ9-THC, the major psychoactive constituent of the cannabis plant, with evidence of their agonist activity at CB1 cannabinoid receptors.

1.4. There is also increasing evidence of their human psychoactivity and of associated health harms, including neurological (e.g. somnolence), cardiovascular (e.g. rapid heart rate, increased blood pressure, palpitations, chest pain), gastrointestinal (e.g. nausea and vomiting, abdominal pain), psychiatric (e.g. anxiety, hallucinations, delirium, psychosis, panic attacks) and ocular (mydriasis, red eyes, blurred vision) effects. There are also reports of withdrawal symptoms. Materials with psychoactivity similar to that of Δ9-THC are liable to have similar effects on psychomotor activity, for example, on driving ability. As with many other illicitly produced substances, there may also be health risks from contaminants or from by-products of manufacture.

1.5. More severe effects have occasionally been reported such as tonicclonic seizures, metabolic acidosis and rhabdomyolysis. Some affected people have required hospital admission and occasionally mechanical ventilation. Adverse effects have also been reported to affect children and adolescents. Serious toxicity, however, appears uncommon and to date there have been very few UK detections reported in people experiencing clinical toxicity or drug-related deaths, although these are likely to be underestimated by current limitations in sample testing. The possibility that some of the reported adverse effects might be caused by co-used substances cannot be excluded.

1.6. Much of the information on health harms is preliminary and uncontrolled and often lacks analytical confirmation. Coupled with the pharmacological evidence of cannabimimetic effects, however, it does, provide sufficient indication of a potential risk to public health to justify control of selected psychoactive compounds under the MDA. Those compounds currently providing the highest risk are those that have already been detected in the UK, especially HHC in view of the frequency of detection. Other structurally related compounds, however, are likely to appear in the UK in the future, especially those that have already been detected in other countries.

1.7. It was not previously thought necessary to control THCA as this is a component of the cannabis plant that is already controlled. In view of its recent appearance of THCA in drug markets as pure material (‘diamonds’) in solid form for smoking or in liquids for vaping, control of THCA is now necessary.

1.8. For the hydrogenated forms of CBD such as H4-CBD, there is currently less evidence of psychoactivity and health harms and insufficient justification for control of via the MDA at present. Any emerging evidence of the psychoactivity of these compounds, however, should be kept under review.

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

Recommendation 1a

The following compounds should be included as named compounds in the MDA as Class B and in the MDR as Schedule 1 compounds. They should also be listed in Schedule 1 of the Misuse of Drugs (Designation) (England, Wales and Scotland) Order 2015.

Hexahydro-derivatives

• Hexahydrocannabinol (HHC)
• Hexahydrocannabiphorol (HHCP)
• Hexahydrocannabihexol (HHCH)
• 9-Hydroxyhexahydrocannabinol (9-OH-HHC)
• 10-Hydroxyhexahydrocannabinol(10-OH-HHC)
• 11-Hydroxyhexahydrocannabinol (11-OH-HHC)
• 10-Hydroxyhexahydrocannabiphorol (10-OH-HHCP)
• Hexahydrocannabinol-C8 (HHC-C8)
• Hexahydrocannabinol-C9 (HHC-C9)

THC derivatives

• 11-Hydroxy tetrahydrocannabinol (11-OH-THC)

THC precursors (cannabinoid acids)

• Tetrahydrocannabinolic acid A (THCA-A)
• Tetrahydrocannabinolic acid B (THCA-B)

Note that:

(a) Chemical names are given in Annex A of the report.

(b) There are also potential harms associated with Hexahydrocannabinol-Oacetate (HHC-acetate, HHCO-acetate) and Hexahydrocannabiphorol acetate (HHCPO-acetate). It is not necessary to list the acetates separately, as these will automatically be covered by the ‘esters and ethers’ clause in the legislation.

Recommendation 1b

Following appropriate consultation, the UK generic text for cannabinoids in the MDA should be updated so that psychoactive SSCs that are not currently captured are included in the MDA as Class B and in the MDR as Schedule 1 compounds. They should also be listed in Schedule 1 of the Misuse of Drugs (Designation) (England, Wales and Scotland) Order 2015.

Suggested alterations to the current cannabinoid generic text are provided in Annex D of the report.

Lead: Home Office.

Measure of outcome: The inclusion of the described compounds in Class B of the Misuse of Drugs Act 1971 and Schedule 1 of the Misuse of Drugs Regulations 2001 by adjustment of the cannabinoid generic (following appropriate consultation) or as named compounds.

Recommendation 2

More detailed information on the legal status and adverse effects of SSCs should be made available to people who use drugs, the public and staff who may encounter drug users, especially those working in health, and social care.

The public facing websites “Frank” (England), “Know the Score” (Scotland) and “DAN24/7” (Wales) do not appear to include information about these compounds and should be updated to include this, especially for those compounds already prevalent in the UK.

The National Police Chief’s Council has established a cannabis edibles group which provides information to parents. This may be a useful way to pass on information to parents about SSCs, their adverse health effects and their legal status.

Information should be provided to schools about the illicit substances that may be found in vapes, their legal status and their potential adverse health effects.

Retailers of vapes and other products that may contain SSCs should be provided with information about their legal status.

Healthcare professionals can register to access comprehensive evidencebased online information and clinical management advice about potentially toxic substances, including illicit drugs, via the TOXBASE website, provided by the National Poisons Information Service (NPIS) and funded by the UK Health Security Agency (UKHSA). While TOXBASE provides information about THC, cannabis and SCRA, searches for the SSC described in this report yield negative results. Information about the SSCs described in this report should be included

Leads: Office for Health Improvement and Disparities, National Poisons Information Service, UK Health Security Agency, Betsi Cadwaladr University Health Board, Scottish Government Population Health Directorate, National Police Chief’s Council, Department for Business and Trade, Department for Education, Scottish Government – Learning Directorate, Welsh Government – Department for Education and Welsh Language, Department of Education (Northern Ireland).

Measure of outcome: Communication of appropriate online and written information to target groups.

Recommendation 3

The status of H4-CBD under the PSA should be established using the standard in vitro testing panel.

Leads: Home Office

Measure of outcome: Availability of panel testing report.

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

Yours sincerely,

[Signed]

Professor Owen Bowden-Jones

Chair of the ACMD

[Signed]

Professor Simon Thomas

Chair of the ACMD NPS Committee