Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation

Peter McCulloch; Hannah Family; April Shaw; Gabriele Vojt; Gail Gilchrist; Catriona Matheson; Margaret Maxwell; Joanne Neale; Gareth Myring; Hugh McLeod; Matthew Hickman; Peter Vickerman; Alison Munro; Steve MacGillivray

doi:10.1016/j.drugpo.2026.105174

Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation

Peter McCulloch^*, Hannah Family, April Shaw, Gabriele Vojt, Gail Gilchrist, Catriona Matheson, Margaret Maxwell, Joanne Neale, Gareth Myring, Hugh McLeod, Matthew Hickman, Peter Vickerman, Alison Munro, Steve MacGillivray

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

Abstract

Background:

Understanding the factors that hinder or support engagement with Opioid Agonist Therapy (OAT) and Needle and Syringe Provision (NSP) is essential for increasing retention and reducing drug-related harm. This study comprised a multimethod realist evaluation to develop a theory of the factors influencing service provision, focusing on access, engagement, retention, and successful exit (clients outcome met) from services.

Design:

Phase 1 involved an online survey of UK drug and alcohol service commissioners, focus groups with interest holders, and a qualitative systematic review to build an initial programme theory of optimal service provision. Phase 2 tested and refined this theory through 86 in-depth interviews across three UK sites with commissioners, managers, staff, and people who use services (both regular attendees and those with limited contact).

Results:

The Realist Evaluation identified five interrelated contexts (Agency and Empowerment; Self-esteem and Respect; Knowledge and Communication; Goals, Needs and Preferences; and Resources and Demands), within which mechanisms can shape optimal service provision. Person-centred approaches, low-threshold access, and timely provider contact foster agency. Confidentiality, non-stigmatising care, and strengths-based support build self-esteem, while skilled staff, training, and peer networks enhance knowledge and communication. Flexible appointments, integrated services, and shared stakeholder responsibility align care with individual goals and needs. Adequate staffing, training, supervision, and sustainable funding enable responsive, resilient services.

Conclusions:

These findings show how interacting relational and structural mechanisms generate optimal outcomes, guiding policy and service design. Implementing a multi-agency approach, integrating different mechanisms across the identified contexts, may be necessary to achieve optimal service delivery.

Original language	English
Article number	105174
Number of pages	13
Journal	The International journal on drug policy
Volume	150
Early online date	20 Feb 2026
DOIs	https://doi.org/10.1016/j.drugpo.2026.105174
Publication status	Published - 1 Apr 2026

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Publisher Copyright:
© 2026 The Authors. Published by Elsevier B.V.

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McCulloch, P., Family, H., Shaw, A., Vojt, G., Gilchrist, G., Matheson, C., Maxwell, M., Neale, J., Myring, G., McLeod, H., Hickman, M., Vickerman, P., Munro, A., & MacGillivray, S. (2026). Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation. The International journal on drug policy, 150, Article 105174. https://doi.org/10.1016/j.drugpo.2026.105174

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title = "Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation",

abstract = "Background:Understanding the factors that hinder or support engagement with Opioid Agonist Therapy (OAT) and Needle and Syringe Provision (NSP) is essential for increasing retention and reducing drug-related harm. This study comprised a multimethod realist evaluation to develop a theory of the factors influencing service provision, focusing on access, engagement, retention, and successful exit (clients outcome met) from services. Design:Phase 1 involved an online survey of UK drug and alcohol service commissioners, focus groups with interest holders, and a qualitative systematic review to build an initial programme theory of optimal service provision. Phase 2 tested and refined this theory through 86 in-depth interviews across three UK sites with commissioners, managers, staff, and people who use services (both regular attendees and those with limited contact). Results:The Realist Evaluation identified five interrelated contexts (Agency and Empowerment; Self-esteem and Respect; Knowledge and Communication; Goals, Needs and Preferences; and Resources and Demands), within which mechanisms can shape optimal service provision. Person-centred approaches, low-threshold access, and timely provider contact foster agency. Confidentiality, non-stigmatising care, and strengths-based support build self-esteem, while skilled staff, training, and peer networks enhance knowledge and communication. Flexible appointments, integrated services, and shared stakeholder responsibility align care with individual goals and needs. Adequate staffing, training, supervision, and sustainable funding enable responsive, resilient services. Conclusions:These findings show how interacting relational and structural mechanisms generate optimal outcomes, guiding policy and service design. Implementing a multi-agency approach, integrating different mechanisms across the identified contexts, may be necessary to achieve optimal service delivery.",

author = "Peter McCulloch and Hannah Family and April Shaw and Gabriele Vojt and Gail Gilchrist and Catriona Matheson and Margaret Maxwell and Joanne Neale and Gareth Myring and Hugh McLeod and Matthew Hickman and Peter Vickerman and Alison Munro and Steve MacGillivray",

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McCulloch, P, Family, H, Shaw, A, Vojt, G, Gilchrist, G, Matheson, C, Maxwell, M, Neale, J, Myring, G, McLeod, H, Hickman, M , Vickerman, P, Munro, A & MacGillivray, S 2026, 'Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation', The International journal on drug policy, vol. 150, 105174. https://doi.org/10.1016/j.drugpo.2026.105174

TY - JOUR

T1 - Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP)

T2 - a realist evaluation

AU - McCulloch, Peter

AU - Family, Hannah

AU - Shaw, April

AU - Vojt, Gabriele

AU - Gilchrist, Gail

AU - Matheson, Catriona

AU - Maxwell, Margaret

AU - Neale, Joanne

AU - Myring, Gareth

AU - McLeod, Hugh

AU - Hickman, Matthew

AU - Vickerman, Peter

AU - Munro, Alison

AU - MacGillivray, Steve

PY - 2026/4/1

Y1 - 2026/4/1

N2 - Background:Understanding the factors that hinder or support engagement with Opioid Agonist Therapy (OAT) and Needle and Syringe Provision (NSP) is essential for increasing retention and reducing drug-related harm. This study comprised a multimethod realist evaluation to develop a theory of the factors influencing service provision, focusing on access, engagement, retention, and successful exit (clients outcome met) from services. Design:Phase 1 involved an online survey of UK drug and alcohol service commissioners, focus groups with interest holders, and a qualitative systematic review to build an initial programme theory of optimal service provision. Phase 2 tested and refined this theory through 86 in-depth interviews across three UK sites with commissioners, managers, staff, and people who use services (both regular attendees and those with limited contact). Results:The Realist Evaluation identified five interrelated contexts (Agency and Empowerment; Self-esteem and Respect; Knowledge and Communication; Goals, Needs and Preferences; and Resources and Demands), within which mechanisms can shape optimal service provision. Person-centred approaches, low-threshold access, and timely provider contact foster agency. Confidentiality, non-stigmatising care, and strengths-based support build self-esteem, while skilled staff, training, and peer networks enhance knowledge and communication. Flexible appointments, integrated services, and shared stakeholder responsibility align care with individual goals and needs. Adequate staffing, training, supervision, and sustainable funding enable responsive, resilient services. Conclusions:These findings show how interacting relational and structural mechanisms generate optimal outcomes, guiding policy and service design. Implementing a multi-agency approach, integrating different mechanisms across the identified contexts, may be necessary to achieve optimal service delivery.

AB - Background:Understanding the factors that hinder or support engagement with Opioid Agonist Therapy (OAT) and Needle and Syringe Provision (NSP) is essential for increasing retention and reducing drug-related harm. This study comprised a multimethod realist evaluation to develop a theory of the factors influencing service provision, focusing on access, engagement, retention, and successful exit (clients outcome met) from services. Design:Phase 1 involved an online survey of UK drug and alcohol service commissioners, focus groups with interest holders, and a qualitative systematic review to build an initial programme theory of optimal service provision. Phase 2 tested and refined this theory through 86 in-depth interviews across three UK sites with commissioners, managers, staff, and people who use services (both regular attendees and those with limited contact). Results:The Realist Evaluation identified five interrelated contexts (Agency and Empowerment; Self-esteem and Respect; Knowledge and Communication; Goals, Needs and Preferences; and Resources and Demands), within which mechanisms can shape optimal service provision. Person-centred approaches, low-threshold access, and timely provider contact foster agency. Confidentiality, non-stigmatising care, and strengths-based support build self-esteem, while skilled staff, training, and peer networks enhance knowledge and communication. Flexible appointments, integrated services, and shared stakeholder responsibility align care with individual goals and needs. Adequate staffing, training, supervision, and sustainable funding enable responsive, resilient services. Conclusions:These findings show how interacting relational and structural mechanisms generate optimal outcomes, guiding policy and service design. Implementing a multi-agency approach, integrating different mechanisms across the identified contexts, may be necessary to achieve optimal service delivery.

U2 - 10.1016/j.drugpo.2026.105174

DO - 10.1016/j.drugpo.2026.105174

M3 - Article (Academic Journal)

C2 - 41722213

SN - 0955-3959

VL - 150

JO - The International journal on drug policy

JF - The International journal on drug policy

M1 - 105174

ER -

Optimal provision of opioid agonist therapy (OAT) and needle and syringe programmes (NSP): a realist evaluation

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