Impact of Medicare Part D opioid safety policies on high-risk, non-elderly Medicare beneficiaries - Representing ~3% of the U.S. population, high-risk, non-elderly Medicare beneficiaries account for ~25% of overdose deaths and hospitalizations related to prescription opioids. Among this population, opioid-related harms are concentrated in the 20-25% who are prescribed long- term opioid therapy, primarily for chronic pain. We will first examine effects of a recent, important policy intervention – Medicare Part D opioid safety edits – on an understudied cohort of high-risk, non-elderly beneficiaries who are prescribed long-term, high-dose opioid therapy (Aim 1). Effective January 1, 2019, Medicare Part D plans are required to incorporate a set of enhanced safety edits into their drug utilization review systems. The most salient is a “care coordination edit” alerting pharmacists when daily doses of opioid prescriptions exceed 90 morphine milligram equivalence. The new Medicare Part D opioid safety policy is intended to identify overprescribing through pharmacist-prescriber consultation without directly restricting patient access (intended beneficial effect). It may also encourage the initiation of buprenorphine for opioid use treatment in lieu of high-dose opioid regimes (beneficial spillover effect). However, the possible misinterpretation of the 90-MME threshold as a “hard stop”, coupled with administrative burdens, may prompt rapid dose reduction and abrupt discontinuation (unintended detrimental effect). Furthermore, some key subgroups may be less likely to benefit from the Medicare Part D opioid safety policy and more susceptible to unintended harms (Aim 2). The Medicare Part D opioid safety policy initially evolved against the backdrop of the public health emergency declared in 2020. To minimize potential disruptions to health care, the federal government made temporary changes to the Medicare telehealth and opioid regulations, which may have facilitated beneficial effects of the Medicare Part D opioid safety policy and alleviated detrimental policy effects (Aim 3). We will use 2017-22 Medicare claims data and a quasi-experimental research designs to accomplish our Aims. We will assess appropriate opioid tapering (intended beneficial effect), inappropriate opioid tapering (unintended detrimental effect), buprenorphine initiation (beneficial spillover effect), and opioid-related adverse events in emergency department and inpatient settings (downstream effect). We aim to: 1. Examine effects of the first-year, pre-public health emergency implementation of the Part D opioid safety policy on high-risk, non-elderly beneficiaries who are prescribed long-term, high-dose opioid therapy; 2. Compare how key subgroups were differentially affected by the Medicare policy effects; 3. Extend Aims 1 and 2 to the pre- and post-public health emergency periods to elucidate the interaction of the Medicare Part D opioid safety policy with flexibilities provided during the 2020 public health emergency and beyond. Our findings will enable policymakers to develop nuanced policies and practices tailored to the high-risk, non-elderly population and key subgroups.