Implantable Naltrexone for Opioid Dependence

Naltrexone is a long-acting opioid antagonist approved in the US, in oral form, for the treatment of opioid dependence. However, its utility has been hampered by poor adherence. To determine whether naltrexone pellets implanted subcutaneously reduce opioid self-administration and reduce craving, researchers from Norway conducted an open-label randomized trial comparing naltrexone implants with usual care (i.e., referral to after-care services) among 56 adults with opioid dependence. All participants had completed an abstinence-oriented inpatient treatment program, and all had passed an oral naltrexone challenge. Outcomes between the 2 groups were assessed at 6 months.

• Patients randomized to receive implantable naltrexone reported 18 days with heroin use versus 37 days for patients in the control group. The implantable naltrexone group reported 37 days with any opioid use (including methadone or buprenorphine) versus 97 days in the control group. Hair analysis, conducted in 43 of the 56, patients was concordant with self-report in 86% percent of cases.

• Polydrug use, injection drug use, and craving were lower in the naltrexone group compared with controls; however, no significant differences in overdose, depression, criminal activity, outpatient treatment attendance, and use of alcohol or nonopioid drugs were detected between groups.

• One overdose death occurred in each treatment group. Implants were removed from 3 patients in the naltrexone group (1 due to site infection, 1 due to site pain, and 1 due to diarrhea). There were no attempts to remove the implant by subjects.

Comments:

This small open-label randomized study demonstrated a reduction in opioid use with implantable naltrexone compared to usual care at 6 months. Larger trials among more diverse patients, with longer follow-up and other naltrexone formulations are warranted to determine the appropriate candidates, the long-term benefits, and the incidence of adverse events with such treatment.

Alexander Y. Walley, MD, MSc

Reference:

Kunøe N, Lobmaier P, Vederhus JK, et al. Naltrexone implants after in-patient treatment for opioid dependence: randomised controlled trial. Br J Psychiatry. 2009;194(6):541–546.