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

New research from the National Pharmaceutical Council finds 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 analysis says the changes affected millions of beneficiaries and raises new questions about access, outcomes and formulary oversight.

Why it matters: - The findings suggest Medicare beneficiaries are losing coverage for some branded drugs faster than people with commercial insurance. - The coverage shifts affect access across 16 competitive drug classes, where plans can use formulary exclusions to gain leverage on rebates. - The study adds to evidence that post-IRA Part D changes may be producing unintended access effects, not just lower out-of-pocket costs.

What happened: - The National Pharmaceutical Council published an analysis in Health Affairs Scholar titled “Changes in Medicare Part D Coverage in Competitive Classes in the Post-Inflation Reduction Act Landscape: 2024-2026.” - The study compared Medicare standalone prescription drug plans, Medicare Advantage Prescription Drug plans and commercial insurance. - The research examined changes in coverage for brand-only medicines in competitive drug classes from 2024 through 2026. - The analysis used competitive classes defined as those with at least three commercially available, eligible brand-only drugs. - The IRA’s Part D changes, including the cap on patient out-of-pocket costs and increased catastrophic phase liability for plans and manufacturers, took effect Jan. 1, 2025.

The details: - On average, 4.5 million Medicare beneficiaries lost insurance coverage for previously covered branded medicines across the 16 competitive classes. - That total included 2.7 million beneficiaries in standalone PDPs and 1.8 million in MA-PD plans. - Medicare coverage declined in both 2025 and 2026, with larger reductions in 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. - At the drug level, coverage fell from 2024 to 2026 for more than 5% of beneficiaries for over half of the included drugs in PDPs, or 30 of 59 drugs. - Those PDP drug-level declines represented at least 1.14 million fewer covered beneficiaries per drug. - At the class level, average coverage dropped by at least five percentage points from 2024 to 2026 in 10 of 16 classes in PDPs, seven of 16 in MA-PD and three included classes in commercial plans. - The authors say incentives to exclude competing drugs may be strongest in classes with multiple branded prescription drugs.

Between the lines: - The study points to a tradeoff in Part D design: lower patient cost-sharing can come alongside narrower formulary coverage. - The larger drops in standalone PDPs suggest plan structure may affect how aggressively coverage is restricted. - The comparison with commercial plans strengthens the case that the coverage changes are not just a broad market trend. - Dr. Campbell, the study co-author and NPC chief science officer, said the findings are consistent with one of the theorized unintended consequences of the IRA.

What's next: - The authors say more research is needed as IRA implementation continues. - NPC says Medicare patients’ access to medicines, health outcomes and Part D formulary review processes should be monitored. - Future work may show whether the coverage declines continue as more IRA provisions take full effect.

The bottom line: - Medicare Part D plans appear to be narrowing coverage in competitive drug classes more often than commercial insurers, and the access impact is already measurable across millions of beneficiaries. - More information