Long-acting intramuscular naltrexone for opioid use disorder: Utilization and association with multi-morbidity nationally in the Veterans Health Administration.

Background: Long acting intramuscular (IM) naltrexone is an effective treatment for opioid use disorder (OUD), but rates and correlates of its use have not been studied.

Methods: National administrative from the Veterans Health Administration (VHA) from Fiscal Year 2012 identified only 16 VHA facilities that prescribed IM naltrexone to 5 or more veterans diagnosed with OUD. Data from these facilities were used to identify sociodemographic, diagnostic, and service use characteristics, including use of psychotropic medication, that were characteristic of veterans who filled prescriptions for IM naltrexone. This was in comparison to users of opiate agonist treatments (methadone or buprenorphine) or veterans with no pharmacologic treatment for OUD. Comparisons were made using both bi-variate analyses and multivariable logistic regression.

Results: Only 179 of 16,402 veterans with OUD (1%) at these 16 facilities filled a prescription for IM naltrexone and only 256 of 99,394 (0.26%) nationally. These veterans were characterized by past homelessness, co-morbid alcohol use disorder, multiple psychiatric disorders, and a greater likelihood of psychiatric hospitalization, as well as mental health outpatient and antidepressant medication use.

Conclusions: IM naltrexone is rarely used for OUD and is primarily used for patients with multiple co-morbidities, especially alcohol use disorder and serious mental illness. The use of this treatment illustrates many of the principles identified by the emerging focus on multi-morbidity as a critical feature of clinical practice.