NIDA Clinical Trials Network CTN-0051, Extended-Release Naltrexone vs. Buprenorphine for Opioid Treatment (X:BOT): Study design and rationale.

INTRODUCTION: For opioid-dependent patients in the US and elsewhere, detoxification and counseling-only aftercare are treatment mainstays. Long-term abstinence is rarely achieved; many patients relapse and overdose after detoxification. Methadone, buprenorphine-naloxone (BUP-NX) and extended-release naltrexone (XR-NTX) can prevent opioid relapse but are underutilized. This study is intended to develop an evidence-base to help patients and providers make informed choices and to foster wider adoption of relapse-prevention pharmacotherapies.

METHODS: The National Institute on Drug Abuse's Clinical Trials Network (CTN) study CTN-0051, X:BOT, is a comparative effectiveness study of treatment for 24weeks with XR-NTX, an opioid antagonist, versus BUP-NX, a high affinity partial opioid agonist, for opioid dependent patients initiating treatment at 8 short-term residential (detoxification) units and continuing care as outpatients. Up to 600 participants are randomized (1:1) to XR-NTX or BUP-NX.

RESULTS: The primary outcome is time to opioid relapse (i.e., loss of persistent abstinence) across the 24-week treatment phase. Differences between arms in the distribution of time-to-relapse will be compared (construction of the asymptotic 95% CI for the hazard ratio of the difference between arms). Secondary outcomes include proportions retained in treatment, rates of opioid abstinence, adverse events, cigarette, alcohol, and other drug use, and HIV risk behaviors; opioid cravings, quality of life, cognitive function, genetic moderators, and cost effectiveness.

CONCLUSIONS: XR-NTX and BUP-NX differ considerably in their characteristics and clinical management; no studies to date have compared XR-NTX with buprenorphine maintenance. Study design choices and compromises inherent to a comparative effectiveness trial of distinct treatment regimens are reviewed.

CLINICAL TRIAL REGISTRATION: NCT02032433.