WAC, AWP, NADAC, MAC, FUL and ASP compared

In October 2026, retail pharmacies paid an average of about 2.8 cents for a 20 mg atorvastatin tablet, according to the federal government's survey of pharmacy invoices. In November 2013 the same survey put it at 18 cents. Both numbers come from NADAC, the National Average Drug Acquisition Cost, which CMS publishes in weekly files on data.medicaid.gov⁹; GxRadar tracks 47 generics from those files on its price pages.

NADAC is one price for that tablet. A list price set by the manufacturer, a published reference price, a payer's reimbursement ceiling and a federal Medicaid cap may all describe the same pill, and none of them is the amount a patient pays at the counter.

Each benchmark was created by a different party to do a different job. That is why two news stories can quote prices for the same generic that differ by an order of magnitude, and why pharmacy contracts and Medicaid files often seem to be talking about different drugs.

Six benchmarks side by side

WAC and AWP, the list prices

WAC is the manufacturer's list price. CMS, in its Part B payment limits overview¹, defines it as the list price for wholesalers or direct purchasers in the United States, not counting prompt-pay or other discounts, rebates or reductions. It moves when the manufacturer announces a price change, and because it sits before discounts, what buyers end up paying can be lower.

AWP is older and looser. CMS notes in the same document¹ that AWP is set using industry reference sources "as there is no statutory definition." Formulas written as a percentage off AWP were common in pharmacy contracts and in Medicaid. A KFF review⁷ found that in September 2013, 12 states used AWP as their primary Medicaid reimbursement metric, 16 used WAC and only six used actual acquisition cost. Federal programs have mostly moved away from AWP since. Medicare Part B now uses it in narrow cases, paying pneumococcal, influenza, COVID-19 and hepatitis B vaccines at 95 percent of AWP¹.

NADAC, what pharmacies pay

NADAC is the government's estimate of what a retail pharmacy actually pays on the invoice. Under CMS's published methodology⁴, it is built from a monthly random survey of independent and chain pharmacies and updated weekly. It leaves out rebates and discounts that do not appear on the invoice, so a pharmacy's true net cost can be lower. GxRadar's explainers on what NADAC measures and how it is calculated go further into the survey.

NADAC matters mostly because of Medicaid. Since the 2016 Covered Outpatient Drugs rule, described in CMS's letter to state health officials⁵, states must pay for most outpatient drugs at actual acquisition cost plus a professional dispensing fee, and NADAC is one of the main tools they use to set that cost. GxRadar's piece on Medicaid and generic drug prices covers the rest of that system.

MAC and FUL, the payer ceilings

MAC lists are reimbursement ceilings set by whoever is paying the pharmacy. A pharmacy benefit manager running a plan's drug benefit commonly sets a MAC for each generic with several makers, and a state Medicaid program may keep its own. There is no single national MAC; lists differ by payer, are usually not public and can change often. For Medicare Part D, 42 CFR 423.505(b)(21)⁸ requires plan sponsors to update any drug pricing standard on Jan. 1 of each contract year and "not less frequently than once every 7 days thereafter." How those ceilings turn into a pharmacy's payment is traced in how pharmacies get paid.

The FUL is the federal Medicaid version, explained at more length in GxRadar's piece on the federal upper limit. Under 42 CFR 447.514², CMS sets one when FDA rates at least three products as pharmaceutically and therapeutically equivalent. The base amount is 175 percent of the weighted average of the most recently reported monthly AMPs. If that would fall below the average retail acquisition cost from the most current national survey, CMS raises it to match, and CMS uses NADAC for that check. The limit applies in the aggregate across a state's spending, not claim by claim. CMS posts the monthly files on its Federal Upper Limits page³; the current version of the rule took effect on April 1, 2016.

ASP and AMP, the net manufacturer prices

ASP is used mainly for drugs given in a doctor's office or clinic, which Medicare covers under Part B. Manufacturers calculate it for each calendar quarter and submit it no later than 30 days after the quarter ends, using sales to all US purchasers net of many price concessions. The CMS overview¹ says payment limits are usually 106 percent of ASP. When a drug is too new to have ASP data, payment can be based on WAC, at an amount not to exceed 103 percent of WAC.

A seventh number sits behind several of these. AMP, average manufacturer price, is what manufacturers report to CMS for drugs sold to retail community pharmacies. It drives Medicaid rebates and feeds the FUL formula, but it is not published drug by drug, so most readers meet it only indirectly.

FDA economists used it in a December 2019 analysis⁶ of drugs that first went generic between 2015 and 2017, comparing confidential AMP data with invoice prices from a commercial database. The gap between the two, which the authors attributed mostly to wholesaler markups, gives a sense of how much the choice of benchmark moves the answer.

The competition pattern in that table is the subject of GxRadar's analysis of why generic prices fall as competitors enter.

How the six relate to a patient's price

By rule a FUL cannot sit below the NADAC-based acquisition cost, while MAC levels vary by payer and are rarely public. ASP matters little for retail generics because it applies to Part B drugs.

A patient's price sits outside all six. A cash price adds a dispensing charge and the pharmacy's margin to the drug cost, and an insured patient's copay is set by the plan's benefit design; GxRadar's pieces on cash price versus copay and why the same generic costs different amounts pick up from there. NADAC files are refreshed every week, and the next FUL file follows CMS's monthly schedule.