Medicare Part D plans narrow drug coverage more than commercial plans, study finds

New National Pharmaceutical Council research says Medicare Part D plans were more likely than commercial plans to restrict coverage in competitive drug classes after the Inflation Reduction Act took effect. The findings raise fresh questions about beneficiary access as the law’s Part D changes continue to reshape formularies in 2025 and 2026.

Why it matters: - The study suggests Medicare beneficiaries are losing coverage for some branded drugs faster than people with commercial insurance. - The coverage shifts could affect access to therapeutic alternatives in drug classes with multiple branded options. - The findings add to concerns about unintended consequences from the Inflation Reduction Act’s changes to Part D design.

What happened: - National Pharmaceutical Council research published in Health Affairs Scholar analyzed 2024-2026 formulary data across Medicare Part D and commercial plans. - The study examined brand-only medicines in competitive drug classes across Medicare standalone prescription drug plans and Medicare Advantage Prescription Drug plans. - Competitive classes were defined as categories with at least three commercially available, eligible brand-only drugs. - The analysis found broader declines in coverage in Medicare Part D plans after implementation of the Inflation Reduction Act.

The details: - The Inflation Reduction Act changed Part D benefit design beginning Jan. 1, 2025, including a cap on patient out-of-pocket costs and higher catastrophic phase liability for plans and manufacturers. - The research found Medicare coverage declined in both 2025 and 2026, with larger drops in standalone PDPs than in MA-PD plans. - In 2024, the average share of beneficiaries with coverage was 71.4% in commercial plans, 52.3% in MA-PD plans and 47.4% in PDP plans. - The study estimates that 4.5 million Medicare beneficiaries — 2.7 million in PDPs and 1.8 million in MA-PD plans — lost insurance coverage for previously covered branded medicines across 16 competitive classes. - At the drug level, coverage decreases from 2024-2026 affected more than 5% of beneficiaries for 30 of 59 included drugs in PDP plans. - Those PDP drops represented at least 1.14 million fewer beneficiaries covered per drug. - At the class level, coverage declined by at least five percentage points on average from 2024-2026 in 10 of 16 classes in PDPs, seven of 16 in MA-PD plans and three included classes in commercial plans. - The study says incentives to exclude drugs may be highest in classes with multiple branded prescription drugs, where plans can use exclusions to seek higher rebates.

Between the lines: - The results point to a possible tradeoff in the post-IRA market: lower out-of-pocket exposure for some patients, but tighter formularies for others. - Campbell, a study co-author and NPC chief science officer, said beneficiaries are losing coverage for certain drugs at a higher rate than those with commercial insurance and that the pattern is consistent with a theorized unintended consequence of the IRA. - The gap between commercial and Medicare coverage suggests plan design, not just clinical need, is increasingly shaping access in competitive classes.

What's next: - The authors say more research is needed as IRA implementation continues. - The findings support closer monitoring of Medicare patients’ access to medicines and health outcomes. - The study also points to a need to examine whether Part D formulary review processes are adequately protecting access. - NPC says it will continue policy-relevant research on patient access to innovative medicines and scientific advancement.

The bottom line: - Medicare Part D coverage appears to be tightening faster than commercial coverage in competitive drug classes, and the trend could affect access for millions of beneficiaries.