Medicare Part D utilization management for negotiated drugs and within-class comparators, 2019-2026

The Inflation Reduction Act requires Medicare drug plans to cover medications selected for federal price negotiation once negotiated prices take effect, and by 2026 all 10 first-round drugs were covered by every plan. Plans retain the ability to require prior authorization, step therapy, and/or quantity limits as formulary management tools.

Using national Medicare Part D formulary files, 2019-2026, we compared restrictions on 9 of the 10 negotiated medications with those on similar drugs in the same classes not selected for negotiation. Estimates were weighted by plan enrollment.

Weighted by enrollment, step therapy on negotiated diabetes medications fell to zero by 2025 and rose to 5.0% in 2026, while comparators stayed below 1%; negotiated anticoagulants rose to 4.8%. Cost sharing is set by formulary tier rather than by drug and did not change. Prior authorization was near-absent in the cardiometabolic classes and near-universal in the specialty classes, with no change associated with negotiation.

Guaranteed coverage does not guarantee access. In the first year of negotiated prices, universal listing coexisted with a return of step therapy on negotiated cardiometabolic drugs that comparators did not mirror, while what beneficiaries paid at the pharmacy was unchanged.