Pharmacy Reimbursement Models: How Laws Shape Generic Drug Payments

When you pick up a generic prescription at the pharmacy, you might think the price is simple: cheaper than the brand, right? But behind that low copay is a tangled web of federal laws, state regulations, and corporate contracts that determine exactly how much the pharmacy gets paid-and whether they can even afford to fill your prescription. In the U.S., generic drugs make up 90% of all prescriptions but only 23% of total drug spending. That’s the promise: more pills, less cost. But the system that’s supposed to deliver on that promise is full of hidden costs, legal loopholes, and financial pressures that hit pharmacies-and patients-hard.

How Generic Drugs Got Their Reimbursement Rules

The foundation of today’s generic drug system wasn’t built by pharmacists or insurers. It was written into law in 1984 with the Hatch-Waxman Act. This law created a fast-track approval path for generic drugs called the ANDA (Abbreviated New Drug Application). It let companies copy brand-name drugs without repeating expensive clinical trials, as long as they proved bioequivalence. In return, it gave brand-name makers extended patent protection to balance the scales. The goal? Lower prices through competition. And it worked. Today, over 84% of Medicare Part D prescriptions are for generics.

But here’s the catch: the law didn’t fix how pharmacies get paid. That was left to insurers, pharmacy benefit managers (PBMs), and state Medicaid programs. And that’s where things got messy.

Two Ways Pharmacies Get Paid for Generics

There are two main reimbursement models for generic drugs: Average Wholesale Price (AWP) and Maximum Allowable Cost (MAC). AWP used to be the standard-it’s a list price set by manufacturers, often inflated, and pharmacies got paid a percentage off that number. But AWP doesn’t reflect what pharmacies actually pay. So states and Medicare shifted to MAC.

MAC programs set a fixed payment cap for each generic drug based on what pharmacies actually pay to buy it. If the pharmacy buys a pill for $0.30, and the MAC is $0.35, they get $0.35. If they bought it for $0.40? They eat the $0.05 loss. It sounds fair, but MAC lists are updated infrequently. A drug might drop in price overnight, but the MAC stays the same for weeks. Pharmacies get stuck paying more than they’re reimbursed.

And then there’s the brand-to-generic switch. If a doctor writes a brand-name prescription but the pharmacy dispenses the generic (which is legal under substitution laws), the pharmacy still gets paid the MAC rate for the generic-even if the patient’s insurance would’ve covered the brand at a higher rate. That means pharmacies lose money on the difference. Some states require pharmacists to substitute unless the doctor says "do not substitute." Others leave it up to the pharmacist. The rules vary by state, and the financial impact doesn’t.

Who Controls the Money: PBMs and Their Hidden Fees

Behind every prescription claim is a pharmacy benefit manager (PBM). CVS Caremark, Express Scripts, and OptumRX control over 80% of U.S. prescription claims. PBMs don’t just process claims-they negotiate rebates with drugmakers, set formularies, and decide which drugs get covered and at what cost.

Their revenue comes from three places: rebates from manufacturers, spread pricing, and fees from insurers. Spread pricing is the most controversial. It’s the difference between what the insurer pays the PBM and what the PBM pays the pharmacy. For example: the insurer pays the PBM $10 for a generic. The PBM pays the pharmacy $6. The $4 difference? That’s the PBM’s profit. And it’s not disclosed to the pharmacy or the patient.

In 2023, the average reimbursement margin for independent pharmacies on generic drugs was just 1.4%. In 2018, it was 3.2%. That’s not just a drop-it’s a squeeze. Many small pharmacies are losing money on every generic they fill. They’re forced to make up the difference by selling more over-the-counter products or cutting staff hours.

State Laws Trying to Fix the System

Forty-four states have passed laws to regulate PBMs and protect pharmacies. Some require PBMs to pay pharmacies at least the actual acquisition cost of the drug. Others ban gag clauses-those were the rules that prevented pharmacists from telling patients, “This drug is cheaper if you pay cash.” Before 2018, pharmacists couldn’t say a word. Now, in most states, they can. But enforcement is weak. Many patients still don’t know they could save $10 or $20 by paying out of pocket.

States also use Preferred Drug Lists (PDLs) to steer Medicaid patients toward cheaper generics. If a drug isn’t on the list, the pharmacy might get paid less-or not at all. Prior authorization is another hurdle. In 2022, 28% of Medicare Part D plans required prior authorization for at least one generic drug. That means the pharmacist has to call the doctor, wait for approval, and hope the patient doesn’t walk away frustrated.

The Medicare $2 Drug List: A New Experiment

In 2025, the Centers for Medicare & Medicaid Services (CMS) is testing a bold new model: the Medicare $2 Drug List. It’s simple: for about 100 to 150 low-cost, high-use generic drugs, Medicare Part D plans will cap the patient copay at $2. No deductible. No tiering. Just $2.

The drugs on the list aren’t chosen randomly. They’re selected based on clinical guidelines, how often they’re prescribed to Medicare patients, and whether multiple manufacturers make them (to avoid supply issues). Think metformin, lisinopril, atorvastatin-drugs millions of seniors take daily.

This isn’t charity. It’s economics. By making generics predictable and affordable, CMS hopes to improve adherence. Patients who skip pills because they can’t afford them end up in the ER. That costs far more than $2. Early data from grocery chains like Kroger and Walmart-where generics have been $4 or less for years-show higher refill rates and better health outcomes.

If it works, this model could expand. And it might finally align reimbursement with real-world cost.

What’s Next for Generic Reimbursement?

The Inflation Reduction Act of 2022 capped insulin at $35 a month and will cap total out-of-pocket drug costs for Medicare beneficiaries at $2,000 in 2025. That’s huge. But it doesn’t fix the underlying reimbursement structure.

PBMs still control pricing. MAC lists still lag behind market prices. Independent pharmacies still operate on razor-thin margins. And authorized generics-where brand-name companies release their own generic version to block competitors-are still used to delay real competition.

The next big shift might be value-based payment. Instead of paying per pill, insurers could pay based on health outcomes. But that’s years away. In the meantime, pharmacies are stuck between laws that demand generic substitution and reimbursement models that don’t pay enough to make it sustainable.

What This Means for Patients

You might think lower drug prices mean you’re saving money. But if your pharmacy can’t afford to fill your prescription, you’re not getting it at all. Or worse-you’re paying more than you should because the system hides the real cost.

Always ask your pharmacist: “Can I pay cash instead?” Even if you have insurance, the cash price might be lower than your copay. That’s legal now. And if your copay for a generic is over $10, ask why. Is it on the Medicare $2 list? Is it being held up by prior authorization? Is your PBM making a profit off your prescription?

Generic drugs are one of the most effective tools we have to control healthcare costs. But if the system that pays for them doesn’t work, the promise of affordable medicine stays unfulfilled.

What You Can Do

If you’re on Medicare or have insurance, check your plan’s formulary. See which generics are preferred. Ask if your medication is on the Medicare $2 list. Always compare cash prices with your copay. And if your pharmacy seems to be struggling-long lines, limited hours, or staff shortages-it might be because the reimbursement system isn’t working. Talk to your pharmacist. Ask questions. Demand transparency. The system only changes when patients push for it.