BACKGROUND AND AIM: Extended-release naltrexone (XR-NTX) is an underused treatment option for opioid dependence, today only available in a few countries in the world. Although effective, safe and feasible in short-term treatment, long-term data are scarce and there is no recommendation for required treatment length. The aims of the study were to determine the perceived need of long-term XR-NTX treatment and to examine long-term treatment outcomes.

DESIGN: In this prospective cohort study, following a parent 1-year study of XR-NTX, participants received treatment with XR-NTX at their own discretion for a maximum of 104 weeks.
SETTING: Five urban, outpatient addiction clinics in Norway.
PARTICIPANTS: Opioid-dependent adults 18-60 years old (n=50) already participating in the parent study.
INTERVENTION: XR-NTX administrated as intra-muscular injections (380 mg) every 4 weeks.
MEASUREMENTS: Time in the study, use of opioids and other illicit substances, opioid craving, and treatment satisfaction reported every 4 weeks.

FINDINGS: Among 58 participants who completed the 1-year parent study, 50 chose to continue the treatment with XR-NTX. Median prolonged treatment time was 44.0 weeks (95% CI: 25.5-62.5), ranging from 8 to 104 weeks. Most participants (35, 70%) reported no relapse to opioid use during treatment while a subgroup (15, 30%) reported relapses to opioids during the study. Scores for mean treatment satisfaction and recommending treatment to others were very high (>9) and mean opioid craving score was very low (<1) on a scale ranging from 0 to 10.

CONCLUSIONS: Extended-release naltrexone (XR-NTX) was well tolerated in long-term treatment of opioid dependent individuals in Norway already in XR-NTX treatment. On average, the participants chose to continue treatment for almost 1 year beyond the initial 9 to 12 months of treatment. Participants reported high treatment satisfaction and 70% showed no relapse to opioids during the treatment period.