A pharmacy benefit manager, or PBM, is a company that sits between your health insurance plan and the pharmacies and drug manufacturers you rely on. PBMs manage nearly every aspect of your prescription drug coverage: which medications are covered, how much you pay at the counter, and which pharmacies you can use. Three large PBMs (CVS Caremark, Express Scripts, and OptumRx) dominate the market, and their decisions ripple through the entire drug supply chain.
How PBMs Fit Into the Drug Supply Chain
When your doctor writes a prescription and you hand it to a pharmacist, a PBM is working behind the scenes. The PBM processes your claim in real time, checking whether the drug is covered under your plan, applying your copay, and telling the pharmacy how much it will be reimbursed. This happens in seconds, but the rules governing that transaction were negotiated months or years earlier between the PBM, your employer or insurer, drug manufacturers, and pharmacies.
Employers and insurance companies hire PBMs to control drug spending. In theory, PBMs use their massive purchasing power to negotiate lower prices. In practice, the system is far more complicated, and the lack of transparency in PBM contracts has drawn scrutiny from regulators, pharmacists, and lawmakers alike. The Federal Trade Commission released a report in 2024 calling PBMs “powerful middlemen” that may be inflating drug costs and squeezing independent pharmacies.
Building the Formulary
One of the most consequential things a PBM does is create and manage the formulary, which is the list of drugs your insurance plan will cover. Formularies are organized into tiers, and the tier a drug lands on determines what you pay out of pocket. A typical structure has three or four tiers: generic drugs at the lowest copay, preferred brand-name drugs in the middle, and non-preferred or non-formulary brands at the highest cost. In many plans, generic copays run around $5 to $10, preferred brands cost $10 to $15, and non-formulary brands can hit $25 to $30 or more.
PBMs decide which drugs go on which tier based partly on clinical evidence and partly on the rebates drug manufacturers are willing to offer. A manufacturer might offer a larger rebate to get its brand-name drug placed on a preferred tier, which means more patients are steered toward it. This is where things get contentious: the drug that ends up on a lower tier isn’t always the cheapest option at the pharmacy counter. It’s the one whose manufacturer offered the PBM the best deal.
Negotiating Rebates With Drug Makers
Rebate negotiation is the financial engine of the PBM business. When a drug manufacturer wants its product covered by the plans a PBM manages, the PBM negotiates a discount, typically structured as a rebate paid back to the PBM for every unit of the drug dispensed. The PBM then shares all or a portion of that rebate with the health plan or employer that hired it.
How much the PBM keeps versus passes along is one of the most opaque parts of the system. Rebate contracts are highly confidential, and terms are only shared between the contracted parties. Critics argue this secrecy allows PBMs to retain significant portions of rebate revenue. Defenders counter that PBMs pass through the vast majority of rebates and that the confidentiality is standard in competitive negotiations. Either way, the dollar amounts are enormous: rebates on brand-name drugs represent billions of dollars flowing through the system annually.
Controlling Which Drugs You Can Access
Beyond the formulary, PBMs use tools called utilization management to control which prescriptions get filled and under what conditions. The two most common are prior authorization and step therapy.
Prior authorization means your doctor must get approval from the PBM before the pharmacy can dispense certain medications. This typically involves submitting clinical information to justify why the drug is necessary. The process can take 24 hours or longer, and if the request is denied, your doctor can appeal or switch to an alternative the PBM prefers.
Step therapy requires you to try a less expensive drug first before the PBM will cover a more costly alternative. If the first-line medication doesn’t work or causes side effects, your doctor can request an exemption. These requirements are meant to steer prescribing toward cost-effective options, but they can delay treatment and add administrative burden for both patients and physicians. Your doctor’s office often has to fill out forms and provide supporting documentation for each exemption request.
Setting Up Pharmacy Networks
PBMs assemble the networks of pharmacies where you can fill prescriptions under your plan. These networks come in two general types. Open networks include a wide range of pharmacies, giving you more choices but typically at a higher cost per prescription. Preferred networks are more restrictive, limiting you to a smaller group of pharmacies that have agreed to steeper discounts in exchange for higher patient volume.
If you fill a prescription at a pharmacy outside your PBM’s network, you may pay significantly more or receive no coverage at all. This is why your copay can vary depending on which pharmacy you visit, even for the same drug. PBMs negotiate reimbursement rates with each pharmacy in the network, and those rates aren’t always favorable for the pharmacy.
How PBMs Make Money
PBMs generate revenue through several channels, and the pricing model your employer or insurer chose determines which ones are in play.
In a spread pricing model, the PBM charges the health plan one price for a prescription and pays the pharmacy a lower price, keeping the difference as profit. The plan sponsor gets cost predictability because it pays a fixed negotiated rate, but it doesn’t see what the pharmacy actually received. If the pharmacy charges less than the rate the PBM negotiated with the plan, the PBM pockets the margin on every prescription filled.
In a pass-through model, the PBM passes along the exact amount it paid the pharmacy and instead charges the plan an administrative fee per claim. This is more transparent, but administrative fees can be structured in ways that still leave room for significant PBM revenue. Many employers and public plans have been shifting toward pass-through arrangements in recent years as scrutiny of spread pricing has increased.
PBMs also earn revenue from retained rebate portions, fees charged to pharmacies, and payments from manufacturers for services like data analytics and market access.
Impact on Pharmacies
Independent and community pharmacies feel the effects of PBM practices most acutely. One major pressure point is something called DIR fees, which stands for direct and indirect remuneration. These were originally designed to track rebates in the Medicare system, but the term now covers a broad range of post-sale fees that pharmacies must pay back to PBMs after a prescription has already been dispensed.
Because these fees are applied after the sale, pharmacies can’t predict them at the time of dispensing. The result is that a prescription that appeared profitable at the register can end up losing money once the PBM claws back its fees weeks or months later. Research has found that 38% of surveyed pharmacies cut staff numbers or hours to cope with rising DIR fees, and nearly 30% reduced the services they offered.
PBMs also set reimbursement caps for generic drugs using what are called Maximum Allowable Cost lists. These lists cap what the PBM will pay a pharmacy for a given generic medication, regardless of what the pharmacy actually paid its supplier. MAC prices are updated frequently and are influenced by how long a drug has been available as a generic, how many manufacturers produce it, and whether there have been supply disruptions. When MAC reimbursement rates fall below a pharmacy’s acquisition cost, the pharmacy loses money on every prescription it fills for that drug.
Why PBMs Are Controversial
The core tension is straightforward: PBMs were created to reduce drug costs, but their critics argue the industry’s structure now does the opposite. The three largest PBMs are each owned by a parent company that also owns an insurance plan and a pharmacy chain or mail-order operation. This vertical integration means the same corporate entity can decide which drugs are covered, negotiate the price, and fill the prescription, raising concerns about self-dealing. In some state Medicaid markets, a single PBM controls more than 70% to 80% of prescriptions.
Confidential rebate contracts make it difficult for employers, patients, or regulators to determine whether PBMs are genuinely reducing costs or redirecting savings to their own bottom line. Patients sometimes pay copays based on a drug’s list price rather than its post-rebate price, meaning they don’t benefit from the discounts the PBM negotiated on their behalf. And the administrative requirements PBMs impose, from prior authorizations to step therapy, can create real delays in care, particularly for patients with complex or urgent conditions.