Average Manufacturer Price is the weighted average net price that retail community pharmacies, and the wholesalers supplying them, actually pay a drug manufacturer, and it is the figure that drives Medicaid drug rebates. Every quarter, each manufacturer with a National Drug Rebate Agreement owes state Medicaid programs a per-unit rebate calculated directly from AMP. Those rebates run into the tens of billions of dollars a year, and the same AMP number also caps what Medicaid will pay pharmacies for many generic drugs.
What AMP Actually Measures
Section 1927(k)(1) of the Social Security Act defines AMP as the average price paid to a manufacturer for a covered outpatient drug by two groups: wholesalers distributing to retail community pharmacies, and retail community pharmacies buying directly from the manufacturer.1Social Security Administration. Social Security Act 1927 – Payment for Covered Outpatient Drugs It is a weighted average, so large-volume transactions move the number more than small ones, and it is calculated per National Drug Code at the nine-digit level. Each package size and strength gets its own AMP.
The number is meant to reflect the true net price at the retail counter, not list price. Manufacturers subtract cash discounts, volume discounts, charge-backs, and other concessions that pass through to retail community pharmacies. They then strip out categories of sales that would distort the retail picture: sales to the Indian Health Service, the Department of Veterans Affairs, the Department of Defense, 340B covered entities, hospitals, long-term care and hospice pharmacies, clinics, mail-order pharmacies, managed care organizations, and pharmacy benefit managers, among others.2eCFR. 42 CFR 447.504 – Determination of Average Manufacturer Price Customary prompt-pay discounts to wholesalers and bona fide service fees are also excluded by statute.1Social Security Administration. Social Security Act 1927 – Payment for Covered Outpatient Drugs
A retail community pharmacy, for this purpose, is a licensed pharmacy open to the general public. Pharmacies restricted to a specific population — a managed care plan’s members, a hospital’s patients, a nursing home’s residents — do not count.3Cornell Law Institute. 42 USC 1396r-8 – Retail Community Pharmacy Definition Specialty pharmacies are included only if they meet that same open-to-the-public test.
The Rebate Formula for Brand-Name Drugs
To have their drugs covered by state Medicaid programs, manufacturers must sign a National Drug Rebate Agreement with the Secretary of Health and Human Services, committing them to pay quarterly rebates on units dispensed to Medicaid beneficiaries.4Medicaid. Medicaid Drug Rebate Program For single-source and innovator multiple-source drugs (brand-name products), the basic unit rebate amount is the greater of two figures:
- 23.1 percent of AMP per unit, or
- The difference between AMP and the manufacturer’s “best price” per unit.
Blood clotting factors and drugs approved exclusively for pediatric use use a lower minimum of 17.1 percent of AMP but otherwise follow the same formula.5Medicaid. Unit Rebate Amount Information
Best price is the lowest price the manufacturer offers to any commercial buyer in the United States during the rebate period, with certain government prices excluded. The interaction with AMP is what gives the program its bite. A manufacturer that quietly offers a private buyer a deep discount widens the gap between AMP and best price, and Medicaid’s rebate rises to match that gap. Selling cheap to one commercial customer forces a matching concession to every state Medicaid program.
The Inflation Add-On
For brand-name drugs the manufacturer also owes an additional rebate whenever the drug’s AMP has risen faster than inflation. CMS compares the drug’s baseline AMP from its market-entry quarter against the current quarter’s AMP, adjusted by growth in the Consumer Price Index for All Urban Consumers. If current AMP has outpaced CPI-U, the manufacturer owes the excess on top of the basic rebate; if it has not, the additional rebate is zero.6Medicaid. Unit Rebate Amount Calculation for Single Source or Innovator Multiple Source Drugs For drugs with a history of aggressive price increases, this inflation piece can be far larger than the basic rebate.
Generics: A Flat Percentage of AMP
Non-innovator multiple-source drugs — generics — follow a simpler track. The unit rebate is a flat, lower minimum percentage of AMP, and there is no best-price comparison to worry about.5Medicaid. Unit Rebate Amount Information Generics are also subject to an inflation-based additional rebate under the same CPI-U mechanism used for brand-name drugs.
Nominal-Price Sales
Sales priced below 10 percent of AMP are treated as “nominal” and excluded from AMP so that charitable or public-health giveaways do not drag the average down artificially.7Centers for Medicare & Medicaid Services. Medicaid Drug Pricing Regulation Summary For best-price purposes, the nominal-price exemption is limited to sales to 340B covered entities, intermediate care facilities for individuals with intellectual disabilities, and state-owned or state-operated nursing facilities.
AMP Also Caps Generic Reimbursement
AMP does a second job beyond rebates. Under the Affordable Care Act, the Federal Upper Limit on what Medicaid will pay pharmacies for a multiple-source generic drug must be at least 175 percent of the weighted average of the most recent monthly AMPs for all therapeutically equivalent versions of that drug.8Medicaid. Federal Upper Limit When that 175 percent figure comes in below actual pharmacy acquisition cost, as measured by a national survey, CMS can use a higher multiplier to close the gap. Accurate AMP submissions therefore affect not just what manufacturers pay out in rebates but what pharmacies collect on the reimbursement side.
Drugs That Do Not Fit the Retail Model: 5i
Some drugs almost never move through a retail pharmacy. Products administered by inhalation, infusion, instillation, implant, or injection — the “5i drugs” — are typically given in physician offices or hospitals. If 70 percent or more of a 5i drug’s monthly unit sales go to entities other than retail community pharmacies and their wholesalers, the manufacturer uses a parallel 5i AMP methodology. That version includes sales to hospitals, clinics, managed care organizations, and physician offices, along with the discounts and rebates flowing through those channels. Government and 340B prices, foreign sales, and sales to prisons remain excluded. Quarterly AMP for a 5i drug is the sum of the three monthly AMPs, whichever method applied in each month.
What Manufacturers Must Report, and What Happens If They Get It Wrong
Manufacturers file AMP data with CMS electronically at the nine-digit NDC level. Monthly AMP is due no later than 30 days after the end of the reported month. The quarterly report, which also carries best price, customary prompt-pay discount totals, and nominal-price sales figures, is due within 30 days after the end of the calendar quarter.9eCFR. 42 CFR 447.510 – Requirements and Penalties for Manufacturers A designated corporate officer must certify the submissions.
Late or inaccurate filings can trigger civil monetary penalties, and CMS has the authority to suspend a manufacturer’s National Drug Rebate Agreement for repeated failures. Suspension is severe: without an active agreement, state Medicaid programs will not cover the manufacturer’s drugs. With Medicaid covering roughly one in four Americans, that is a market almost no drug company can afford to lose, which is why AMP calculation and reporting sit at the center of pharmaceutical compliance work.