Comparative efficacy of naltrexone-accelerated versus sublingual buprenorphine in opioid withdrawal management and initiating injectable naltrexone treatment: study protocol for a randomized controlled trial

Background Extended-release injectable naltrexone (XR-NTX), a long-acting opioid antagonist, is an effective relapse prevention strategy in the treatment of opioid use disorder (OUD). However, standard XR-NTX initiation requires completion of opioid withdrawal management and a 1–2 week opioid-free period. This interval is associated with heightened vulnerability to lapse and relapse, and many patients fail to initiate XR-NTX treatment successfully. Therefore, alternative strategies that enable rapid XR-NTX initiation are needed. This study aimed to compare the effectiveness and safety of naltrexone-accelerated (NA) versus sublingual buprenorphine (SB) withdrawal management in facilitating XR-NTX initiation among patients with OUD. Methods This single-center, open-label, randomized controlled trial uses a parallel-group design. Eligible patients aged 18–60 years with moderate to severe OUD who are actively using opioids and are not receiving regular maintenance treatment with methadone or buprenorphine are randomly assigned to one of two groups: (1) NA withdrawal management, comprising one day of adjunctive non-opioid medications, one day of buprenorphine administration, one day of washout, and four days of gradual oral naltrexone titration (1, 3, 12, and 25 mg/day); or (2) SB withdrawal management, comprising one day of adjunctive non-opioid medications, six days of buprenorphine tapering (up to 8 mg on Day 2, 6 mg on Day 3, 4 mg on Days 4–5, 2 mg on Day 6, and 1 mg on Day 7), and a seven-day washout period. Adjunctive non-opioid medications in both groups comprised clonidine, clonazepam, gabapentin, and trazodone. The primary outcomes are the proportions of participants who (1) achieve a negative urine drug test for the assessed opioids and (2) receive XR-NTX at the end of the withdrawal management period. Secondary outcomes include severity of withdrawal symptoms, opioid craving intensity, and adverse effects. All analyses are conducted according to the intention-to-treat principle. Discussion The findings of this trial may provide clinically relevant evidence to support rapid initiation of XR-NTX treatment in patients with OUD and inform clinical practice. Clinical trial registration https://en.irct.ir/trial/81525 , Iranian Registry of Clinical Trials IRCT20250123064499N1.