Research and analysis

Government response to the ACMD’s advice on 2-benzyl benzimidazole and piperidine benzimidazolone opioids (accessible version)

Updated 5 April 2024

Professor Owen Bowden-Jones,
Chair, Advisory Council on the Misuse of Drugs (ACMD)
Professor Simon Thomas,
Chair of the NPS Committee, ACMD
C/o 1st Floor,
Peel Building
2 Marsham Street
London
SW1P 4DF

By email only: ACMD@homeoffice.gov.uk

February 2023

Dear Owen and Simon,

I am grateful to the ACMD for their advice on 2-benzyl benzimidazole and piperidine benzimidazolone opioids.  Please accept my apologies for the delay in responding to the council.

I have set out each recommendation and the government’s response below.

Recommendation 1

The following compounds should be added to Class A of the Misuse of Drugs Act 1971, consistent with the classification of other potent opioids. As these materials have no medical use it is recommended that they should be placed in schedule 1 of the Misuse of Drugs Regulations 2001 (as amended).

• Metonitazene

• Protonitazene

• Isotonitazene

• Butonitazene

• Flunitazene

• Metodesnitazene (metazene)

• Etodesnitazene (etazene)

• N-Pyrrolidino-etonitazene (etonitazepyne)

• N-Piperidinyl-etonitazene (etonitazepipne)

• Brorphine

Government response

The government accepts this recommendation, with the addition of N-Desethylisotonitazene, included in the ACMD’s addendum advice to the report and will implement this when Parliamentary time allows.

Recommendation 2

The following compounds should be deleted from Schedule 2 and added to Schedule 1 of the Misuse of Drugs Regulations 2001 (as amended):

• Etonitazene

• Clonitazene

Government response

The government accepts this recommendation and will implement this when Parliamentary time allows.

Recommendation 3

The ACMD recommends that a consultation should be undertaken with stakeholders, including academia and the chemical and pharmaceutical industries on the introduction of a generic control on 2-benzyl benzimidazole variants, as new examples may be encountered and could present a serious risk of harm.

Following this consultation, materials covered by the generic should be added to Class A of the Misuse of Drugs Act 1971, consistent with the classification of other potent opioids. As these materials have no medical use it is recommended that they should be placed in Schedule 1 of the Misuse of Drugs Regulations 2001 (as amended).

The proposed wording for the generic for addition to the Misuse of Drugs Act is as follows:

• Any compound (not being a compound for the time being specified in paragraph (a) above) structurally derived from 2-[(2-benzyl)-benzimidazol- 1-yl]ethanamine by modification in any of the following ways, that is to say:

  • (i) By substitution at the nitrogen of the ethanamine to any extent by alkyl substituents containing up to three carbon atoms or alkenyl substituents containing up to three carbon atoms or by inclusion of the nitrogen atom (and no other atoms of the side chain) in a cyclic structure.

  • (ii) By substitution in the phenyl ring of the benzyl system to any extent by alkyl containing up to four carbon atoms, trifluoromethyl, alkoxy containing up to four carbon atoms, trifluoromethoxy, acetyloxy, hydroxy, cyano, thioalkyl containing up to four carbon atoms, alkylsulphonyl containing up to four carbon atoms or halogen substituents.

  • (iii) By substitution at the 5- or 6- positions of the benzimidazole system by nitro, acetyl, cyano, methoxy, trifluoromethyl or halogen substituents.

  • (iv) By substitution at the benzylic carbon by a methyl group.

  • (v) By replacement of the benzylic carbon by a nitrogen, oxygen or sulphur atom.

These modifications are subject to a maximum molecular mass of any derived compound of 500 atomic mass units.

Note: Should evidence emerge of any variants of brorphine appearing, a further generic control, requiring a similar consultation, should be considered.

Government response

The government agrees with this recommendation and will seek to consult relevant interested parties, including academia and the chemical and pharmaceutical industries. The Home Office will update the ACMD on the results of this.

Recommendation 4

In light of the continuing emergence of NPS and particularly synthetic opioid NPS, a working group should be established to consider and provide recommendations on a UK-wide minimum standard set of post-mortem toxicology tests for apparent drug-related deaths, to include testing for relevant novel psychoactive substances to improve consistency of analysis and detection. The best practice recommendations agreed would include standards for reporting.

This working group should include (but not necessarily be limited to) representation from the following:

• Chief Coroner’s Office for England and Wales

• Coroners Service for Northern Ireland

• Crown Office and Procurator Fiscal Service Scotland

• UK and Ireland Association of Forensic Toxicologists

• London Toxicology Group

• Faculty of Forensic and Legal Medicine

• Office for Health Improvement and Disparities

• Home Office Forensic Early Warning System

• Police

• Local drug-related deaths review partnerships

• The ACMD

Government response

The government agrees with the principle of this recommendation. However, given that coroners are independent judicial office holders and independent in the discharge of their statutory functions, it would not be appropriate for the government to seek to establish minimum standards for post-mortem toxicology tests. However, we would encourage coroners to consider this recommendation carefully and we will continue to raise this with relevant officials, including those in devolved governments.

Recommendation 5

Adequate funding should be made available by government to allow coroners, procurators fiscal and forensic toxicologists to follow the best practice guidelines developed via recommendation 4.

Government response

The government will carefully consider funding implications in the event of new guidelines being proposed as the result of the process recommended in this report.

Recommendation 6

Information for health professionals (such as TOXBASE) and the general public (such as Frank) on the health effects of NSO should be reviewed and updated, ensuring that information is available in an appropriate format on NSO compounds including benzimidazole and piperidinyl benzimidazolone opioids and the risks that result from the inclusion of compounds of varying and sometimes very high potency in heroin preparations and counterfeit medicines.

Government response

The government agrees with this recommendation and both Toxbase and FRANK have been updated with advice about the health effects of new synthetic opioids, including benzimidazole opioids.

I am grateful to the ACMD for their detailed report and trust that they find the government’s consideration of their recommendations helpful.

Rt Hon Chris Philp MP

Minister of State for Crime, Policing and Fire