Background and aims: Extended-release naltrexone (XR-NTX), a μ-opioid receptor antagonist for prevention of relapse to opioid dependence, has demonstrated efficacy compared with placebo and comparative effectiveness with buprenorphine-naloxone. We report outcomes for XR-NTX in Vivitrol's Cost and Treatment Outcomes Registry.

Design: Observational, open-label, single-arm, multi-center registry assessing baseline characteristics and clinical and health-related quality-of-life outcomes associated with XR-NTX treatment in clinical practice.

Setting: 32 US treatment centers from 2011 to 2013.

Participants: Patients with opioid dependence who were prescribed XR-NTX treatment and then enrolled into the registry.

Measurements: Monthly visits were evaluated for the full population and for patient ubgroups retrospectively, defined by injection number, focusing on the period between baseline and month 6 (1-, 2/3- or 6-XR-NTX).

Findings: Of 403 enrolled patients, 395 were analyzed. Most patients (n = 349) received out-patient care. On average, patients received five injections (median = 3; range = 1-25). The median number of injections administered within 6 months was higher in patients who at baseline were employed (three versus two unemployed, P = 0.02) or had private insurance (five versus two self-payment, P = 0.005; versus two state-funded, P < 0.001). The 1-, 2/3- and 6-XR-NTX groups had 132, 152 and 111 patients, respectively. At baseline, the 6-XR-NTX patients were more likely to meet normal/minimal mental illness criteria and attend school and less likely to report recent drug use. Within 6 months, the 6-XR-NTX group demonstrated improvements in employment, mental health and psychosocial functioning, and decreases in opioid craving, drug use and drug-related behavior.

Conclusions: Among opioid-dependent people receiving XR-NTX treatment, better mental health, higher education and lower recent drug use at baseline are associated with greater treatment duration; in turn, longer treatment duration is associated with lower relapse rates and improved outcomes generally.

Keywords: Extended-release naltrexone; Vivitrol; medication assisted treatment; opioid dependence; opioid use disorder; registry.

Objective:

The oral formulation of the opioid antagonist naltrexone has shown limited effectiveness for treatment of opioid use disorder due to poor adherence. Long-acting injection naltrexone (XR-naltrexone), administered monthly, circumvents the need for daily pill taking, potentially improving adherence, and has been shown to be superior to placebo in reducing opioid use over 6 months of treatment. This open-label trial compared the outcomes of patients with opioid use disorder treated with XR-naltrexone or oral naltrexone in combination with behavioral therapy.

Method:

Sixty opioid-dependent adults completed inpatient opioid withdrawal and were transitioned to oral naltrexone. They were stratified by severity of opioid use (six or fewer bags versus more than six bags of heroin per day) and randomly assigned (1:1) to continue treatment with oral naltrexone (N=32) or XR-naltrexone (N=28) for 24 weeks. The first dose of XR-naltrexone (380 mg) was administered prior to discharge, with monthly doses thereafter, and oral naltrexone was given in a 50-mg daily dose. All participants received weekly behavioral therapy to support treatment and adherence to naltrexone.

Results:

A Cox proportional hazards model adjusting for race, gender, route of use, and baseline opioid use severity indicated that significantly more patients were retained in treatment for 6 months in the XR-naltrexone group (16 of 28 patients, 57.1%) than in the oral naltrexone group (nine of 32 patients, 28.1%) (hazard ratio=2.18, 95% CI=1.07, 4.43).

Conclusions:

Patients receiving XR-naltrexone had twice the rate of treatment retention at 6 months compared with those taking oral naltrexone. These results support the use of XR-naltrexone combined with behavioral therapy as an effective treatment for patients seeking opioid withdrawal and nonagonist treatment for preventing relapse to opioid use disorder.