Opioid Substitution Therapy (OST) implicated deaths and prescribing: evidence review

1. Introduction

Opioid Substitution Therapy (OST) is the most common treatment for people with opioid dependence and has a substantial evidence base for effectiveness in achieving positive outcomes.^[1] OST medications, methadone and buprenorphine, have been included in the WHO XIV Edition of the Model List of Essential Medicines.^[2] In most cases, treatment will be required for several years or even throughout life. The aim of treatment services in such instances is not only to reduce or stop opioid use, but also to improve health and social functioning, and to help patients avoid some of the more serious consequences of drug use.^[3]

A 2013 independent expert review for the Chief Medical Officer for Scotland found consistent evidence that OST is an effective and internationally used treatment for opioid dependency, which should remain a central component of treatment in Scottish services.^[4] Nevertheless, OST medications – both methadone and buprenorphine – have been implicated in an increasing number and percentage of drug related deaths in recent years, almost always alongside other drugs.

While there is good evidence that the health of individuals with opioid dependence is safeguarded while in substitution treatment, prescribing of OST also carries risks. Evidence shows elevated mortality risks during the first four weeks of starting treatment and the first four weeks after leaving treatment.^[5] This demonstrates that these are critical intervention points to support people in treatment and to prevent drug-related deaths. Evidence also indicates that it is important to consider medication choice and that optimum dose for an individual is critical to achieving positive outcomes.^[6] A further key factor known to support positive outcomes for individuals is the quality of therapeutic relationships.^{[7] [8]}

Improving Medication Assisted Treatment (MAT), access, choice and support has been prioritised by the Scottish Government's National Mission on drug-related deaths, with the introduction of MAT Standards in May 2021. This was accompanied by a commitment from Scotland's Chief Medical Officer to further invest in long-acting buprenorphine.^{[9] [10]} The standards provide a framework to ensure that MAT is sufficiently safe, effective, acceptable, accessible and person-centred to enable people to benefit from high-quality treatment for as long as they need.^[11]

The purpose of this paper is to summarise current knowledge of trends around methadone and buprenorphine-related deaths and changes to prescribing practice – particularly in the context of the COVID-19 pandemic response. The paper also sets out plans for further research and development in this area.

This paper has been produced by the Scottish Government Health and Social Care Analysis Division with support of the drug teams from Public Health Scotland (PHS).