The results of an open-label trial in the American Journal of Psychiatry suggest that naltrexone, an opioid antagonist, had higher adherence rates as a monthly injection than as a daily oral formulation.

The effectiveness of oral naltrexone has proven limited, with clinicians citing low adherence rates. Researchers have prioritized formulations that patients can stick to more easily, including implants tested with some success in Russia and Australia.

The authors of the study identified 60 opioid-dependent adults (18-60 years old) who met the criteria for opioid dependence according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Patients were grouped by frequency of heroin use (up to 6 bags per day or more than 6 bags per day) and were randomly assigned to oral naltrexone at 50 mg/day (n=32) or injectable naltrexone at 380 mg/month (n=28). All participants received weekly behavioral therapy to bolster treatment adherence and effectiveness.

At the conclusion of the 24-week clinical trial, 57.1% (n=16) of patients receiving monthly injections had adhered to the treatment compared with 28.1% (n=9) in the oral formulation group (hazard ratio, 2.18; 95% CI, 1.07-4.43). Oral naltrexone adherence rates were similar to those found in previous studies. The authors recommended that injections be administered over oral naltrexone “other than perhaps for very select cases with a high likelihood of adherence.”

The authors noted limitations of the study related to participant recruitment, including patient preference for agonist vs antagonist treatment. The study began with a weeklong inpatient stay, a challenge for patients with families or without access to paid leave.

The authors of this study reported financial relationships with Alkermes.

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Reference

Sullivan M, Bisaga A, Pavlicova M, et al. A randomized trial comparing extended-release injectable suspension and oral naltrexone, both combined with behavioral therapy, for the treatment of opioid use disorder [published online October 19, 2018]. Am J Psychiatry. doi: 10.1176/appi.ajp.2018.17070732