Aims To review evidence on the effectiveness of opioid maintenance treatment (OMT) in prison and post-release.

Methods Systematic review of experimental and observational studies of prisoners receiving OMT regarding treatment retention, opioid use, risk behaviours, human immunodeficiency virus (HIV)/hepatitis C virus (HCV) incidence, criminality, re-incarceration and mortality. We searched electronic research databases, specialist journals and the EMCDDA library for relevant studies until January 2011. Review conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results Twenty-one studies were identified: six experimental and 15 observational. OMT was associated significantly with reduced heroin use, injecting and syringe-sharing in prison if doses were adequate. Pre-release OMT was associated significantly with increased treatment entry and retention after release if arrangements existed to continue treatment. For other outcomes, associations with pre-release OMT were weaker. Four of five studies found post-release reductions in heroin use. Evidence regarding crime and re-incarceration was equivocal. There was insufficient evidence concerning HIV/HCV incidence. There was limited evidence that pre-release OMT reduces post-release mortality. Disruption of OMT continuity, especially due to brief periods of imprisonment, was associated with very significant increases in HCV incidence.

Conclusions Benefits of prison OMT are similar to those in community settings. OMT presents an opportunity to recruit problem opioid users into treatment, to reduce illicit opioid use and risk behaviours in prison and potentially minimize overdose risks on release. If liaison with community-based programmes exists, prison OMT facilitates continuity of treatment and longer-term benefits can be achieved. For prisoners in OMT before imprisonment, prison OMT provides treatment continuity.