Is extended release naltrexone superior to buprenorphine-naloxone to reduce drinking among outpatients receiving treatment for opioid use disorder? A secondary analysis of the CTN X:BOT trial.

Background The randomized X:BOT trial showed that following induction, sublingual agonist (buprenorphine-naloxone, BUP-NX) or antagonist injection (extended release naltrexone, XR-NTX) produced similar benefits for reducing opioid relapse in injection users with opioid use disorder. Given that XR-NTX reduces drinking in alcohol use disorder (AUD), we completed a secondary analysis of the X:BOT sample of patients successfully inducted onto treatment to determine if XR-NTX (n=204) was superior to BUP-NX (n=270) to reduce drinking or heavy drinking in patients with opioid use disorder. Methods Timeline follow-back recorded standard drink units consumed. Mixed-models regression examined monthly frequencies of any drinking or heavy drinking over 6 months of treatment and proportional hazard survival examined time to first drink. Results Both treatment groups reduced drinking from baseline to post-treatment (small to medium effect), but no differences between groups were detected. However, only 29% (n=136) of the sample had AUD and 19% (n=26/136) of those were abstinent before treatment. Analysis of a subsample enriched for possible drinking included n=136 with an AUD diagnosis plus n=43 who did not have AUD, but reported at least one day of heavy drinking prior to study. Even so, this subsample still reported only 32% of days of any drinking with a median of only 13% of days designated as "heavy". Within this subsample, the BUP-NX group reported greater mean drinks per drinking day than did the XR-NTX group at baseline (p=0.03); however, there were no other significant group differences in drinking observed before, during, or at the end of treatment. Conclusions An overall improvement in drinking occurred for treatment of OUD using both agonist and antagonist approaches indicating that the hypothesis that XR-NTX would be superior to BUP-NX was not supported. The study is limited by low levels of comorbid AUD or heavy drinking observed in X:BOT trial participants seeking treatment for opioid use disorder.