State drug caps associated with fewer Medicaid-covered prescriptions for opioid use disorder, 2017-2022.

The Medicaid program is the largest payer of opioid use disorder (OUD) treatment, including medications for OUD (MOUD). Because of budget neutrality requirements, some Medicaid programs use prescription drug caps to limit the monthly number of prescriptions an enrollee can fill. This study examined the association between Medicaid prescription drug caps and Medicaid-covered prescriptions for 2 forms of MOUD (buprenorphine and naltrexone) from 2017 to 2022 using fee-for-service and managed care data from Medicaid's State Drug Utilization Data. Ten states had monthly prescription drug caps, ranging from 3 to 6 prescriptions. Using multivariate linear regression, we estimated that enrollees in states with monthly drug caps filled 1489.3 fewer MOUD prescriptions per 100 000 enrollees. Further, compared with states with the smallest drug caps (3 drugs), enrollees in states with 4-, 5-, and 6-drug caps filled significantly more prescriptions per state-quarter (907.7, 562.6, and 438.9 more prescriptions, respectively). Our results were robust to sensitivity analyses. Monthly prescription drug caps were significantly associated with a reduction in Medicaid-covered MOUD prescriptions. Medicaid enrollees who need MOUD may be affected by indiscriminate prescription drug cap policies, potentially hindering ongoing efforts to mitigate the opioid crisis.