Identifying Extended-Release Naltrexone Treatment for Opioid Use Disorder in US Medicaid Data.

PURPOSE: Extended-release naltrexone (XR-NTX, monthly injection) is used to treat opioid use disorder (OUD). In claims data, XR-NTX may be identified by drug or procedure codes. In the US, Medicaid is a predominant payer of OUD treatment and differences in state Medicaid policies may produce variation in XR-NTX coding. We aimed to describe documentation of XR-NTX in multi-state Medicaid data. METHODS: Using 2016-2019 National Medicaid data (TAF) from 26 states, we identified individuals with an XR-NTX specific drug or procedure code and evidence of OUD during ≥ 5 months continuous Medicaid enrollment (N = 26 169). At the individual's first observed XR-NTX treatment, we described state-level variation in the types of codes, file source, and presence of procedure codes for injection (including nonspecific codes). RESULTS: An XR-NTX drug code was the first record of treatment for 98% of patients; this percentage was high in all states except one. Just 25% of patients had a procedure code for injection (XR-NTX specific code or non-specific injection code) during the first treatment with marked variation across states, ranging from 7% to 87%. The percentage of patients with evidence of a second XR-NTX treatment was higher among patients with an injection code at initial treatment (61%) than among patients without an injection code (49%). CONCLUSIONS: We found inconsistent patterns of XR-NTX codes across states indicating claim-based definitions should consider both drug and procedure codes to fully capture XR-NTX service delivery. Multiple definitions should be considered in sensitivity analyses given substantial variability in coding practices across states.