Changes in Medication Use After Medicare Part D Annual Out-of-Pocket Spending Caps

How did prescription drug use change after the Inflation Reduction Act implemented annual out-of-pocket spending caps in Medicare starting in 2024?In this cohort study using a difference-in-differences framework of 3053 medications covering 92.9% of gross Medicare Part D spending in 2023, prescriptions for medications paid by Medicare increased after the out-of-pocket cap was implemented in 2024 compared with those paid by commercial insurance; this change was most pronounced among the highest-cost medications, with a 22.7% increase in 2024-2025.Results of this study suggest that implementing annual out-of-pocket caps in Medicare was associated with higher use of medications and that the policy improved Medicare-insured patients’ access to costly medications.

Corresponding Author: Christopher L. Cai, MD, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital, 1620 Tremont St, Ste 3030, Boston, MA 02120 (chrislcai@gmail.com).

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