The research is being led by the University of Stirling in collaboration with researchers from the Universities of Bristol, Aberdeen, Edinburgh, and Lancaster, along with clinical specialists at three Scottish health boards – NHS Greater Glasgow and Clyde, NHS Lanarkshire and NHS Tayside.
The three-year study, funded by the National Institute for Health and Care Research (NIHR), is to be conducted across seven sites in Scotland and England, beginning in January, and is one of the first of its kind.
It will assess whether prescribing a stable dose of diazepam alongside additional support can help prevent harmful drug use and reduce drug-related deaths.
The launch of the trial has been welcomed by the Drugs and Alcohol Policy Minister of Scotland, Maree Todd, who said it will provide an evidence base as efforts continue to save and improve lives.
Benzodiazepines are medicines commonly prescribed to treat anxiety and sleep problems in the short term. However, their use alongside opioids such as heroin is widespread among people who use street drugs, and this combination has been strongly linked to the high rate of drug-related deaths.
While opioid dependency can be safely managed through opioid agonist treatment (OAT) with methadone or buprenorphine, there is currently no equivalent treatment for people dependent on benzodiazepines.
This gap in care has contributed to the increasing use of unpredictable and often dangerous street-sourced benzodiazepines, which can contain unknown or highly potent substances, and are associated with blackouts, overdose and death.
Key area of risk
Professor Catriona Matheson, of the University of Stirling’s Centre for Healthcare and Community Research (CHeCR), is leading the study. She said: “There is a real need for clinically based research within this stigmatised and under-researched population. They should have the same access to evidence-based treatment options available across other areas of healthcare in the UK.
“One of the aims of this research is to address that lack of evidence in such a key area of risk relating to drug-related deaths. It will inform clinical guidance for drug treatment services that have struggled to support people using multiple substances due to the lack of evidence. If successful it will contribute to reducing drug-related deaths, which are a societal challenge.
“Furthermore, the associated health economic analysis will provide evidence of the most cost-effective treatment option. This is essential for ensuring public money is spent appropriately.
“By providing clear clinical and cost effectiveness data our trial will provide commissioners, who are responsible for understanding the local needs for drug treatment and recovery services, and policymakers with direction of what services should be commissioned and how.”
Matthew Hickman, Professor in Public Health and Epidemiology at the NIHR Health Protection Research Unit in Evaluation and Behavioural Science at the University of Bristol, said: “We have shown in other studies that keeping people in opioid agonist treatment is critical to prevention of drug related deaths in the population. This study has the potential both to keep people engaged in treatment and reduce the harms associated with multiple drug use.”
Evidence base
The University of Stirling-led trial builds on previous research that developed a new intervention co-designed with people who have lived experience of benzodiazepine use, and with clinicians.
Participants in the trial will be randomly assigned to receive either a new intervention or standard care, which currently involves a reducing diazepam dose over a maximum of six months as per national guidance.
The new intervention combines a steady prescribed dose of diazepam (up to 30 mg) with tailored psychological and harm reduction support addressing underlying causes such as anxiety, trauma, and sleep difficulties.
Over a 12-month follow-up period, researchers will measure the use of high-risk street benzodiazepines through laboratory analysis of mouth swabs and self-reported data on drug use. Additional outcomes will include overdoses, hospital admissions, mental health measures, cognitive function, and overall treatment acceptability.
Dr Jenny Scott, Senior Lecturer at the Centre for Academic Primary Care, University of Bristol said: “Most drug-related deaths involve a mix of substances, often including benzodiazepines and opioids like heroin. Many ‘street benzos’ aren’t what people think they are - tests show they can contain dangerous and unexpected ingredients. While there’s strong research on treating opioid dependence, there’s very little on benzodiazepine dependence. The InBOAT trial will help us find out whether prescribing benzodiazepines can play a role, and whether starting with a maintenance dose or a detox approach works best to help people stop taking potentially lethal street benzos.”
Drugs and Alcohol Policy Minister of Scotland, Maree Todd, said: “We want to make sure everyone gets the treatment they need. I welcome this trial, which follows a successful Scottish Government-funded feasibility study. It will help provide an evidence base as we continue to strive to save and improve lives.”
Economic impact
The economic impact of the intervention will be determined by examining service use across both study groups, determining whether the approach offers good value for money. Working with a specialist testing centre, the team will monitor emerging synthetic drugs in the street supply to ensure ongoing safety and relevance of testing protocols.
At three and 12 months, participants and clinical staff will take part in interviews to share their experiences and perspectives, helping the researchers understand what makes the new intervention effective, or identify barriers that might limit its success.
The £2.6 million trial has been funded by the NIHR’s Health Technology Assessment programme in response to a commissioned call. It follows a successful feasibility study funded by the Scottish Government Chief Scientist Office.