Switching to extended-release naltrexone (XR-NTX) after 3 months of receiving buprenorphine-naltrexone (BP-NLX) may be as effective as XR-NTX from treatment onset in attaining opioid abstinence and treatment completion at 9 months, according to a prospective study published in Addiction.

In a previous study in which patients with opioid dependence (n=159) were randomly assigned to receive XR-NTX (n=80) or BP-NLX (n=79) after tampering to a 4 mg maximum dose of buprenorphine, both treatments were found to be comparable in maintaining abstinence from heroin in the short term.

In this 9-month prospective cohort analysis, investigators followed patients from the initial study to assess the long-term safety and efficacy of XR-NTX. Patients from this cohort either continued XR-NTX treatment (n=54) or switched to XR-NTX after 3 months of receiving BP-NLX (n=63). The Addiction Severity Index, European version, was used to evaluate treatment retention, substance use, and adverse effects every 4 weeks.

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XR-NTX (380 mg intramuscular injections) was administered to patients every 4 weeks. After 9 months, 49.6% of patients enrolled in the prospective cohort had completed treatment, with 28 participants completing 12 months of treatment in the continued XR-NTX group and 30 participants completing 9 months of treatment in the group receiving XR-NTX. During the study period, 53.7% and 44.4% reported abstaining from opioids in the continuing XR-NTX and inducted XR-NTX groups, respectively.

Use of heroin and other illicit opioid medications was similar in both groups (heroin: mean difference, 0.3; [95% CI, −0.5 to 1.0; P =.479]; other substances: mean difference, 0.7 [95% CI, −0.1 to 1.6; P =.088]) during the 48-week study period. Participants who did not complete treatment were more likely to report higher opioid use at 16 weeks compared with completers (P =.018). At week 48, a greater number of patients in the inducted group reported heavy alcohol use (mean difference, −0.9; 95% CI, −1.8 to −0.02; P =.044).

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Study limitations include the fact that investigators were not blinded to treatment and that the study had an open-label design.

Findings from this small study indicate the “feasibility for induction and continuation of XR-NTX treatment in a clinical setting,” concluded the study authors.

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Solli KK, Latif ZE, Opheim A, et al. Effectiveness, safety and feasibility of extended-release naltrexone for opioid dependence: a nine-month follow-up to a three-month randomized trial [published online May 28, 2018]. Addiction. doi: 10.1111/add.14278