Patients with Opioid Use Disorder Choosing Treatment with Extended-Release Naltrexone: A 6-Month Naturalistic Study.

Introduction: The treatment efficacy of extended-release naltrexone (XR-NTX) for opioid use disorder (OUD) has been demonstrated in several studies, but not in naturalistic settings where opioid agonist treatment (OAT) is freely accessible. This study aimed to examine the different treatment outcomes of XR-NTX in a setting where the participants freely chose XR-NTX as a treatment option instead of OAT.

Methods: This was a 24-week open-label clinical prospective cohort study conducted in an outpatient setting at five hospitals in Norway. The study included 161 participants aged 18-65 years with OUD. Intramuscular injections of XR-NTX were administered every 4 weeks for 24 weeks. Measurements included retention in treatment, reasons for treatment discontinuation, days of use of opioids, other illicit substances and alcohol, level of heroin craving, treatment satisfaction, and adverse events (AEs).

Results: Of 161 included participants, the mean age was 38 years, and 24% were women; 138 received at least one dose of the study medication (modified intention-to-treat [MITT] population), and mean time in treatment was 18.1 weeks (95% CI: 16.8-19.4). The majority of the MITT population (84; 60.9%) completed 24 weeks of treatment in the study. There was a significant decrease in the overall use of opioids (p < 0.001) and the use of alcohol, and other illicit substances were low. The participants generally reported high treatment satisfaction and low heroin cravings. Those who completed the 24 weeks of treatment reported significantly fewer days of opioid use (p < 0.001) and higher treatment satisfaction (p < 0.001) than those who discontinued treatment before 24 weeks. No serious AEs were directly related to XR-NTX use.

Conclusion: This study demonstrated high retention rates, decreased opioid use, and low use of other illicit substances and alcohol. Participants also reported low cravings for heroin and high treatment satisfaction. Completion of the full 24-week treatment resulted in lower opioid use and increased treatment satisfaction compared to those who discontinued treatment before 24 weeks. The observed higher retention and reduced opioid use, compared to other studies, may be attributed to participants' strong motivation for opioid abstinence facilitated by XR-NTX treatment.