Nunes EV, et al. - Given the emergence of extended-release formulations of naltrexone as efficient treatment options for opioid use disorder, researchers conducted this post-hoc analysis investigating the temporal correlation between episodes of opioid use and subsequent dropout in a placebo-controlled trial of extended-release injection naltrexone (XR-NTX) to form presumptions concerning the mechanism by which extended blockade of opioid receptors translates into clinical effectiveness. In this 24-week multiple-site, double-blind, randomized trial of monthly XR-NTX vs placebo injections, 250 adults with opioid use disorder who had completed inpatient detoxification were included. Findings support the efficacy of XR-NTX in reducing the risk of dropout from opioid use disorder treatment after an episode of opioid use. Across the trial, no opioid-positive urine tests were evident in approximately a third of patients (31%) on XR-NTX. However, the trial did not confirm the hypothesis that this would differ from placebo (20%).