Estimating Rebates and Other Discounts Received by Medicare Part D

Abstract

Importance: Spending in Medicare Part D continues to increase. Yet, studies of Medicare Part D are plagued by a common limitation: none can fully account for confidential rebates and other discounts that drug manufacturers and pharmacies pay to Medicare Part D plans. Objectives: To review existing methods and to propose an approach for estimating rebates and other discounts received by Medicare Part D. Evidence Review: Publicly available data from the Boards of Trustees of the Federal Hospital Insurance and Federal Supplementary Medical Insurance Trust Funds, the Centers for Medicare & Medicaid Services, the Medicare Payment Advisory Commission, the Congressional Budget Office, the Government Accountability Office, and the Office of Inspector General. Findings: Existing methods for estimating rebates and other discounts in Medicare Part D have several limitations. This analysis used an approach that aims to improve on those methods. Based on this approach, estimated discounts on brand-name drugs increased in Medicare Part D from 25.4% of gross brand-name spending in 2014 to 37.3% in 2018. There was substantial variation between classes, with estimated 2016 discounts surpassing 50% for some drugs (eg, ophthalmologic and gastrointestinal tract agents) while remaining below 10% for others (eg, antineoplastic and immunologic agents). Between 2014 and 2018, estimated net Medicare Part D spending on prescription drugs increased by 21% from $99 billion to $119 billion. With increasing enrollment, estimated annual net spending per beneficiary remained stable, increasing by just 3% from $2622 to $2694, which was below the 6% rate of inflation during the same period. Conclusions and Relevance: Models that fail to properly account for increasing rebates and other discounts will overestimate Medicare Part D expenditures. Rigorous and transparent methods for estimating discounts are critical for understanding patterns in spending and developing new cost-containment strategies.