Background Illicit drug use is widespread in penal institutions worldwide. Despite this, the use of opioid substitution therapy (OST) in prisons is low. This study evaluates the effectiveness of OST in reducing the negative outcomes associated with opioid abuse among prisoners.

Methods Randomised controlled trials comparing OST with psychosocial therapy or no intervention for opioid dependent prisoners were included. Electronic searches were conducted in: MEDLINE, Embase, CINAHL, PsycINFO and the Cochrane Controlled Trials Register. Two reviewers independently identified relevant papers. Study quality was assessed using the Cochrane risk of bias tool. Pooled RRs were calculated using random effects models (with 95% CI) for opioid use (measured by hair or urine analysis), and re-incarceration after release from prison.

Results Five studies with 820 participants met the inclusion criteria. Allocation concealment was adequate in one study and unclear in four. OST reduced opioid use (3 RCTs, RR 0.78 95% CI 0.64 to 0.95) and re-incarceration (3 RCTs, RR 0.41 95% CI 0.26 to 0.63). Two studies reported a statistically significant reduction in criminal activity and heroin use days, but the data were not pooled because of heterogeneity. Single studies reported statistically significant reductions in syringe sharing, mortality after release, cocaine use and retention in treatment.

Conclusion OST is in effective in reducing many negative outcomes associated with drug use among prisoners, giving far reaching benefits for prisoners, their families and society as a whole. OST should be widely available to prisoners with opioid dependence.