Maintenance on extended-release naltrexone is associated with reduced injection opioid use among justice-involved persons with opioid use disorder.

Introduction: Opioid use disorder (OUD) and injection drug use (IDU) place justice-involved individuals at increased risk for acquiring or transmitting HIV or hepatitis C virus (HCV). Methadone and buprenorphine have been associated with reduced opioid IDU; however, the effect of extended-release naltrexone (XR-NTX) on this behavior is incompletely studied.

Methods: This study examined injection opioid use and shared injection equipment behavior from a completed double-blind placebo-controlled trial of XR-NTX among 88 justice-involved participants with HIV and OUD. Changes in participants' self-reported daily injection opioid use and shared injection equipment was evaluated pre-incarceration, during incarceration, and monthly post-release for 6 months. The study also assessed differences in time to first opioid injection post-release. The research team performed intention to treat and "as treated" (high treatment versus low treatment) analyses.

Results: Fifty-eight of 88 participants (69.5 %) endorsed IDU and 26 (29.5 %) reported sharing injection equipment in the 30 days pre-incarceration; 2 participants (2.2 %) reported IDU during incarceration; 19 (21.6 %) reported IDU one month post-release from prison or jail. Fifty-four (61.4 %) participants had an HIV RNA below 200 copies/mL and 62 (70.5 %) were baseline HCV antibody positive. The 6-month follow-up rate was 49.5 % and 50.5 % for those who received XR-NTX and placebo, respectively, which was not significantly different (p = 0.822). Participants in the XR-NTX and placebo groups had similar low mean opioid injection use post-release and time to first injection opioid use in the Intention-to-treat analysis. In the as-treated analysis, participants in the high treatment group had significantly lower mean proportion of days injecting opioids (13.8 % high treatment versus 22.8 % low treatment, p = 0.02) by month 1, which persisted up to 5 months post-release (0 % high treatment vs 24.3 % low treatment, p < 0.001) and experienced a longer time to first opioid injection post-release (143.8 days high treatment vs 67.4 days low treatment, p < 0.001).

Conclusions: Injection opioid use was low during incarceration and remained low post-release in this justice-involved population. Retention on XR-NTX was associated with reduced intravenous opioid use, which has important implications for reducing transmission of HIV and HCV.