Inflation Reduction Act Changes to Part D Plan Design: Lower Premiums, Higher Deductibles, and Some Smaller Formularies

Following the redesign of Medicare Part D under the Inflation Reduction Act, actual deductibles were higher than predicted based on 2021-2024 trends for both MA-PD plans ($305 vs. $188) and standalone Part D plans ($491 vs. $401). By contrast, premiums were lower than predicted, and Part D plan formularies shrank for protected classes and lower-cost-sharing tiers with no changes in prior authorization, step therapy, or preferred pharmacy network size. The authors conclude that insurers responded to the increased risk-bearing obligations from the Part D redesign primarily by raising deductibles rather than through utilization management or network restrictions, and they call for continued monitoring as the Premium Stabilization Demonstration expires in 2027.