BACKGROUND: Safer smoking equipment interventions for people who smoke crack cocaine have been unevenly implemented globally with most harm reduction policy and practice focused on preventing opioid and injecting related harms. There is a need to synthesise the international evidence on safer inhalation equipment provision for crack and understand how, why, for whom, and in what context can such interventions improve engagement with services, promote safer use practices, and reduce harm.

METHODS: Bibliographic databases (n = 8) and grey literature sources were searched for reports on the distribution of safer inhalation equipment among adults who use crack. Data synthesis was applied around a realist framework, focusing on contextual factors and mechanisms which influenced the interventions' outcomes.

RESULTS: Evidence from 16 peer reviewed and 6 grey literature studies was included. Overall, acceptability of safer inhalation interventions and uptake (≈ 90% in some studies) was high. Evidence pointed towards reduced pipe sharing, decreased injecting, and improved engagement with health and social services. However, implementation was frequently hindered by resource, political, and logistical constraints. Five context-mechanism-outcomes were developed covering service accessibility, integrated provision, tailored provision, peer-supported behaviour change, and organisational resilience against criminalisation and funding cuts. Service engagement and the adoption of safer crack use practices were greater when supportive contexts activate key mechanisms such as perceived safety, ease of access, perceived relevance, and peer-supported learning.

CONCLUSION: Although political, legal and funding constraints can impede implementation and optimal delivery, this review highlights the role of accessible, integrated and peer supported delivery models that services and policymakers can deploy to effectively reduce crack-related health harms and foster engagement with services.