Effectiveness, safety and feasibility of extended-release naltrexone for opioid dependence: a 9-month follow-up to a 3-month randomized trial.

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This is a follow-up study of a previously published randomized clinical trial conducted in Norway that compared extended-release naltrexone (XR-NTX) to buprenorphine-naloxone (BP-NLX) over 3months. At the conclusion of the trial, participants were offered their choice of study medication for an additional 9months. While BP-NLX was available at no cost through opioid maintenance treatment programmes, XR-NTX was available only through study participation, accounting for why almost all participants chose XR-NTX in the follow-up. The aim of this follow-up study was to compare differences in outcome between adults with opioid dependence continuing XR-NTX and those inducted on XR-NTX for a 9-month period, on measures of effectiveness, safety and feasibility. In this prospective cohort study, participants were either continuing XR-NTX, changed from BP-NLX to XR-NTX or re-included into the study and inducted on XR-NTX treatment. Five urban, out-patient addiction clinics in Norway. Opioid-dependent adults continuing (n=54) or inducted on (n=63) XR-NTX. XR-NTX administrated as intramuscular injections (380mg) every fourth week. Data on retention, use of heroin and other illicit substances, opioid craving, treatment satisfaction, addiction-related problems and adverse events were reported every fourth week. Nine-month follow-up completion rates were 51.9% among participants continuing XR-NTX in the follow-up and 47.6% among those inducted on XR-NTX. Opioid abstinence rates were, respectively, 53.7 and 44.4%. No significant group differences were found in use of heroin and other opioids. Opioid-dependent individuals who elect to switch from buprenorphine-naltrexone treatment after 3months to extended-release naltrexone treatment for 9months appear to experience similar treatment completion and abstinence rates and similar adverse event profiles to individuals who had been on extended-release naltrexone from the start of treatment.