Do patient characteristics moderate the effect of extended-release naltrexone (XR-NTX) for opioid use disorder?

Abstract Background Extended release naltrexone (XR-NTX) injected intramuscularly monthly has been shown to reduce relapse in persons with opioid use disorder. Baseline factors, including patients' demographics, comorbidities and lifestyle, may help identify patients who will benefit most or least from XR-NTX treatment. Methods Potential moderators of XR-NTX's effect were examined in the largest North American randomized open-label effectiveness trial of XR-NTX. Relapse status (Yes/No) at 6-month follow-up was regressed on treatment group (XR-NTX, N = 153; or Treatment-as-Usual [TAU], N = 155), baseline covariates, and their two-way interaction to identify moderator effects. Baseline covariates included age, gender, summary scores for depression, suicidal thoughts, drug abuse risk, substance use, medical, psychiatric and employment status, socialization, legal and family/social issues, history of abuse and quality of life measures. Results Alcohol use to intoxication in the 30 days before randomization was a significant moderator: during the treatment phase, those who reported being recently intoxicated before randomization to XR-NTX relapsed to opioids at a rate (56%) similar to TAU (58%), while those without alcohol intoxication in the prior 30 days had a lower rate of opioid relapse (41% vs. 65%, respectively, P < 0.04). Conclusions XR-NTX appeared to work equally well across subgroups with diverse demographic, addiction, mental health and environmental characteristics, with the possible exception of working better among those without recent alcohol intoxication. These findings should be reassuring to practitioners increasingly using XR-NTX as medical addiction therapy in diverse and often vulnerable populations.