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Research Summary

Retention in Naltrexone Implant Treatment: Promising, but Not Conclusive

By increasing adherence, sustained-release formulations of naltrexone are hypothesized to be more effective than oral formulations, which by-and-large have shown little advantage over placebo among opioid-dependent patients. In this observational study from Norway, 61 patients recruited at discharge from medication-free residential drug treatment or prison received sustained-release naltrexone implants lasting 5–6 months. The main outcome measure was retention in treatment, defined as receiving a second implant 4–6 months after the first. Multivariable analyses of pretreatment participant factors associated with retention were also conducted.

  • Thirty-one participants (51%) received a second implant. An additional 6 (10%) initiated opioid maintenance (3 patients) or long-term residential treatment (3 patients).
  • Factors associated with retention included less injection drug use in the 30 days prior to study entry (OR 0.9, p=0.007), duration of longest employment (OR 1.4, p=0.017), and fewer days of worry about family problems (OR 1.7, p=0.034).


Adding to promising evidence from 2 previous trials, this observational noncontrolled study suggests that sustained-release naltrexone may retain patients in treatment at rates approaching those observed in opioid-agonist treatment programs. However, comparative effectiveness trials, with opioid-agonist therapy as the comparison arm, are still needed before widespread use of sustained-release naltrexone can be recommended. Hillary Kunins, MD, MPH, MS


Kunøe N, Lobmaier P, Vederhus JK, et al. Retention in naltrexone implant treatment for opioid dependence. Drug Alcohol Depend. May 28, 2010 [E-pub ahead of print].