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 comparative effectiveness of extended-release naltrexone versus buprenorphine-naloxone for opioid relapse prevention (X:BOT) trial showed that following induction, treatment with the sublingual agonist (buprenorphine-naloxone, BUP-NX) or injected antagonist (extended release naltrexone, XR-NTX) produced similar reductions in opioid relapse in injection users with opioid use disorder (OUD). Because XR-NTX reduces drinking in alcohol use disorder (AUD), we conducted a secondary analysis of the X:BOT sample of patients successfully inducted onto treatment to determine whether XR-NTX (n = 204) was superior to BUP-NX (n = 270) in reducing drinking or heavy drinking in patients with OUD. Methods: Standard drink units consumed were measured using the Timeline Follow-back method. Mixed-models regression was used to examine the monthly frequency of any drinking and heavy drinking over 6 months of treatment. We used a proportional hazard survival analysis to examine the time to first drink. Results: Both treatment groups reduced drinking from baseline to posttreatment (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 136 individuals with an AUD diagnosis plus 43 who did not have AUD, but reported at least one day of heavy drinking prior to the study. However, this subsample reported only 32% of days of any drinking with a median of only 13% of days designated as “heavy.” Within this subsample, at baseline, the BUP-NX group reported more mean drinks per drinking day than the XR-NTX group (p = 0.03); however, there were no other significant group differences on drinking observed before, during, or at the end of treatment. Conclusions: There was an overall reduction in drinking during treatment of OUD using both agonist and antagonist medications, so 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 OUD.