Patient characteristics associated with initiation of XR-naltrexone for opioid use disorder in clinical trials.

BACKGROUND: Extended-release injectable naltrexone (XR-naltrexone) is effective for treatment of patients with opioid use disorder (OUD), but initiation remains a barrier due to the challenge of tolerating opioid withdrawal prior to administration. Understanding factors associated with successful initiation of XR-naltrexone could facilitate its implementation through patient-treatment matching. METHODS: We combined data from five consecutive studies that sought to initiate patients with active opioid use onto XR-naltrexone using a rapid procedure consisting of minimal buprenorphine, non-opioid medications for treating opioid withdrawal, and ascending low doses of oral naltrexone. Associations between patient characteristics and initiating naltrexone were estimated with logistic regression models. To evaluate whether associations differed between inpatient and outpatient settings, patient characteristic-by-setting interactions were also estimated. RESULTS: 409 patients were included in the analyses and 228 (56%) received the first injection. A significantly greater percent of inpatients (62%) vs outpatients (48%) initiated XR-naltrexone. Initiation success was significantly more likely on an inpatient basis for heroin (60.9% inpatient vs 36.2% outpatient), intravenous (56.3% inpatient vs 22.5% outpatient), and speedball users (68.1% inpatient vs 32.3% outpatient). Prescription opioid users showed similar, higher initiation rates across settings (68.9% inpatient; 73.7% outpatient). CONCLUSIONS: An inpatient setting may be the preferred strategy for rapid initiation of XR-naltrexone for opioid users with greater severity, including heroin or speedball injection users or those who use opioids intravenously. Initiation on an outpatient basis may be more likely to succeed for prescription opioid users.

Long-term follow-up study of community-based patients receiving XR-NTX for opioid use disorders.

BACKGROUND AND OBJECTIVES: Extended-release naltrexone (XR-NTX) is FDA-approved to prevent relapse in patients with Opioid Use Disorder. However little is known about long-term use among community-based outpatients. METHODS: Retrospective chart review and long-term follow-up survey among individuals (N = 168) who entered an outpatient XR-NTX trial between 2011 and 2015, during which participants were offered three monthly injections of XR-NTX at no cost. The survey consisted of 35 questions covering a total of four domains: (1) substance use; (2) treatment continuation; (3) barriers; and (4) attitudes. RESULTS: Fifty-seven respondents were successfully surveyed, including 50% of those initially receiving all three XR-NTX injections ("study completers") in the parent study. Study completion was associated with superior outcomes and less likely relapse (defined as daily use), with a much greater time to relapse despite higher rates of concurrent non-opioid substance use. However the majority of participants discontinued treatment with XR-NTX at study completion, largely due to attitudes of "feeling cured" and "wanting to do it on my own" rather than external barriers such as cost or side effects. CONCLUSION: Patients who initiate treatment with XR-NTX might benefit from anticipatory guidance and motivational techniques to encourage long-term adherence as many will experience internal barriers to continuation. Our findings are reassuring that few patients experience side effects or adverse events complicating the effectiveness or safety of long-term use of XR-NTX. SCIENTIFIC SIGNIFICANCE: Among outpatients who successfully receive 3 monthly XR-NTX injections, many will prematurely discontinue treatment due to internal attitudes, such as "feeling cured." (Am J Addict 2017;26:319-325).