Major changes to Medicare Part D, driven by the Inflation Reduction Act, take effect in 2025, including a new $2,000 annual out-of-pocket (OOP) cost cap, the elimination of the coverage gap (donut hole), and the introduction of the Medicare Prescription Payment Plan (MPPP), which allows beneficiaries to spread costs over the year. Additionally, the Manufacturer Discount Program replaces the old discount program, while plans’ and Medicare’s liability shifts, with Part D plans taking on more costs and Medicare’s responsibility decreasing, especially in the catastrophic phase.