Spillover of Medicaid Expansion to Prescribing of Opioid Use Disorder Medications in Medicare Part D

OBJECTIVE: The authors examined whether there were positive spillovers in opioid use disorder medication prescribing to Medicare Part D beneficiaries in Medicaid expansion states. Although prior studies have shown several positive benefits of Medicaid expansion for Americans with opioid use disorder, research has not examined potential spillovers to Medicare beneficiaries who have been hit hard by the opioid crisis. METHODS: Prescribing data were taken from the Medicare Part D Prescription Public Use File (2010-2017). A difference-in-differences linear regression framework was used to identify spillovers in prescribing of buprenorphine and injectable naltrexone to Medicare Part D beneficiaries in Medicaid expansion states. Three sets of dependent variables measured medication prescribing at the county-year level (N=24,850). All models included county and year fixed effects, with standard errors clustered at the state level to address within-state serial correlation. RESULTS: Medicaid expansion was associated with an increase in the probability of a county having an injectable naltrexone provider (p<0.01). After expansion, the number of buprenorphine providers in expansion states increased by 5.6% (p<0.05), and the number of injectable naltrexone providers increased by 3.3% (p<0.01), relative to nonexpansion states. Expansion was associated with a 23.1% (p<0.01) increase in the number of daily doses of injectable naltrexone, relative to nonexpansion states. CONCLUSIONS: Medicaid expansion states may be better equipped to address the opioid crisis because of direct benefits to Medicaid beneficiaries and availability of opioid use disorder medications for Medicare Part D beneficiaries. However, additional efforts are likely needed to close the opioid use disorder treatment gap for Medicare beneficiaries.