Three companies now manage prescription drug benefits for roughly 80 percent of Americans with commercial insurance. That concentration did not happen overnight, and its consequences for generic drug access are only starting to become visible at the pharmacy counter.
How PBM Consolidation Reshaped the Drug Supply Chain
Pharmacy Benefit Managers – the companies that sit between insurers, drug manufacturers, and pharmacies – have spent the past two decades absorbing competitors, acquiring specialty pharmacies, and building vertically integrated empires. CVS Caremark, Express Scripts (owned by Cigna), and OptumRx (owned by UnitedHealth Group) now control the vast majority of prescription claims processing in the United States. When three entities control that much volume, their formulary decisions carry the weight of policy, even without any formal regulatory authority to do so.
Formularies – the lists of drugs a PBM will cover and at what tier – determine whether a patient pays $4 or $140 for the same medication. PBMs construct these lists based on negotiations with drug manufacturers, and in a consolidated market, those negotiations increasingly favor brand-name manufacturers willing to pay large rebates. The rebate system sounds like a discount mechanism, but in practice it can push expensive branded drugs to preferred formulary tiers while cheaper generics get buried under higher copays or removed from coverage entirely.
This is not a theoretical concern. Generic drugs represent a large share of prescriptions filled in the United States by volume, but their share of total drug spending tells a different story. Generics account for a disproportionately small slice of overall drug expenditure, which means brand-name drugs – and the rebates attached to them – are doing heavy financial lifting for PBMs. When a PBM earns more money from a branded drug than a generic alternative, the formulary design will eventually reflect that incentive, regardless of what is best for the patient.
Independent pharmacies have been sounding this alarm for years. Smaller pharmacy operators, already squeezed by low reimbursement rates set unilaterally by PBMs, report being pushed out of preferred pharmacy networks – a status that determines whether a patient can use their local pharmacy without paying a penalty. When patients are steered toward PBM-owned mail-order operations, the generic substitution practices at those facilities are not subject to the same state-level oversight that applies to brick-and-mortar pharmacies. That gap in oversight is where access quietly erodes.
The Formulary Design Problem Nobody Is Talking About
Formulary design has always been opaque. PBMs are not required to publicly disclose the terms of their rebate agreements with manufacturers, which means patients, employers, and even many physicians have no reliable way to know why a specific drug lands on a specific tier. In a fragmented PBM market, that opacity is manageable – different plans compete on formulary quality, and employers can shop around. In a consolidated market, that competitive pressure largely disappears.
The problem is compounded by a practice called “spread pricing,” where a PBM charges an insurer more for a drug than it actually reimburses the pharmacy. On generic drugs, where the actual cost is low, the spread can be proportionally enormous. A generic medication that costs a pharmacy $2 to dispense might be billed to an employer health plan at $15, with the PBM capturing the difference. Because the employer only sees the aggregate billing and not the individual transaction economics, this practice goes undetected for years at a time.
State-level audits have uncovered spread pricing in Medicaid managed care contracts, prompting some states to mandate “pass-through” pricing models where PBMs can only charge what they actually pay. But commercial insurance plans, which cover most working-age Americans, are largely governed by federal ERISA rules that limit state enforcement authority. That federal preemption creates a regulatory blind spot that PBMs have been able to operate within largely undisturbed.
Congress has taken notice, slowly. Legislative proposals requiring PBM transparency have circulated in both chambers, and the Federal Trade Commission launched a study of PBM business practices that drew significant industry pushback. The FTC’s interim report, released in 2022, described the major PBMs as having “significant economic incentives to favor their affiliated pharmacies.” That language is diplomatic. What it describes is a structural conflict of interest that no amount of voluntary disclosure is likely to solve.
For patients managing chronic conditions – diabetes, hypertension, mental health disorders – formulary decisions are not abstractions. A formulary change that moves a generic medication off the preferred tier can add hundreds of dollars annually to out-of-pocket costs. Those costs land hardest on lower-income patients, the same population least likely to have the time or resources to navigate an appeals process. The financial pressure that eroding generic access creates connects to broader economic strain among working Americans – a dynamic also visible in issues like Earned Income Tax Credit delays that squeeze low-wage filers who are already operating on thin margins.
What Employers and Regulators Can Actually Do
Employers who sponsor health plans have more leverage than they typically use. Self-insured employers – which includes most large companies – can demand transparent, pass-through pricing contracts from PBMs and can hire independent auditors to review pharmacy claims data. Some large employers have already moved in this direction, dropping traditional PBM arrangements in favor of direct contracting models or newer transparent PBM entrants. The barrier is not legal; it is institutional inertia and the complexity of renegotiating contracts that took years to build.
Regulatory reform at the federal level would carry far more reach than any employer-by-employer negotiation. Proposals to ban spread pricing in Medicare Part D, require formulary transparency disclosures, and prohibit PBMs from steering patients to affiliated pharmacies without disclosure have all been floated with varying degrees of congressional support. Whether any of them survive the lobbying pressure from an industry that spent heavily on federal influence campaigns over the past decade is the question that patients waiting at the pharmacy counter cannot answer for themselves.
