What Is Maximum Allowable Cost (MAC)?
Maximum Allowable Cost (MAC) is the highest per-unit amount a pharmacy benefit manager (PBM) or health plan will reimburse a pharmacy for a generic or multi-source drug. MAC applies specifically to generics and off-patent branded drugs with multiple bioequivalent alternatives — not to single-source branded medications. The rate is derived from market acquisition data and published on a proprietary MAC list maintained by each PBM.
Consider a practical example: a PBM sets the MAC for a 30-day supply of generic lisinopril 10 mg at $4.00. A pharmacy that sources the drug at $3.20 earns an $0.80 spread before the dispensing fee is added. A pharmacy sourcing the same drug at $4.50 loses $0.50 per fill. The MAC rate is fixed; the pharmacy's sourcing decision determines whether the transaction is profitable.
How Maximum Allowable Cost Works
MAC reimbursement follows a defined sequence:
- List compilation. The PBM builds a MAC list covering eligible generic and multi-source drugs. Inputs typically include NADAC (National Average Drug Acquisition Cost) survey data, wholesaler catalog pricing, and market basket sampling. Exact methodology is proprietary and varies by PBM.
- Price assignment. The PBM assigns a MAC price per unit to each drug on the list.
- Claim submission. The pharmacy dispenses the drug and submits a claim to the PBM.
- Reimbursement determination. The PBM pays the lesser of the MAC rate plus dispensing fee, the pharmacy's usual-and-customary charge, or the plan-specific contracted rate.
- Margin calculation. The pharmacy's margin equals the difference between its actual acquisition cost and the MAC rate received.
MAC lists are updated at the PBM's discretion — some update daily, others weekly or monthly. Several states have enacted MAC transparency laws requiring minimum notice periods before rate changes take effect and establishing formal appeal rights for pharmacies.
Maximum Allowable Cost vs. Average Wholesale Price (AWP)
MAC and AWP are the two most commonly confused drug reimbursement benchmarks, but they govern different drug categories and are set through entirely different processes.
| Dimension | MAC | AWP |
|---|---|---|
| Primary drug category | Generic and multi-source drugs | Brand-name (single-source) drugs |
| How the price is set | Derived from market acquisition data by each PBM | Published list price from drug manufacturers and data publishers |
| Who controls it | Individual PBMs (proprietary) | Drug manufacturers and pricing compendia |
| Transparency | Largely opaque; pharmacy access is limited | Publicly published, though widely criticized as inflated |
| Typical use case | Reimbursement ceiling for generic fills | Starting point for brand reimbursement (AWP minus a discount %) |
AWP is broadly recognized as a published list price that does not reflect actual transaction prices — a distinction that has driven significant industry and regulatory scrutiny. As a practical rule: MAC governs generic reimbursement; AWP governs branded drug reimbursement, typically applied as AWP minus a contractual discount percentage.
MAC in Pharmacy and Payer Contexts
MAC functions differently depending on which side of the transaction you occupy.
- Payer perspective. MAC is the primary cost-control mechanism for generic drug spend. Because generics account for the large majority of prescriptions dispensed in the United States, even small MAC rate adjustments have outsized effects on plan costs.
- Pharmacy perspective. MAC rates directly determine dispensing margin. When a MAC rate falls below a pharmacy's acquisition cost, each fill generates a loss. Independent pharmacies — which typically have less purchasing leverage than large retail chains — are disproportionately exposed to this risk.
- Policy context. MAC opacity is a central driver of PBM reform efforts at both state and federal levels. Spread pricing — where a PBM charges a health plan more than it reimburses the pharmacy, capturing the difference — has drawn scrutiny from CMS and the HHS Office of Inspector General, with MAC lists identified as the mechanism through which spread is generated.
Limitations and Strategic Risks
- Rates can fall below acquisition cost. MAC lists may not update promptly after a market price spike, leaving pharmacies dispensing drugs at a loss until the list is revised.
- No cross-PBM standardization. The same drug can carry materially different MAC prices across plans, creating reconciliation complexity for pharmacies that participate in multiple networks.
- Proprietary opacity. Pharmacies typically cannot access a complete MAC list in advance, making it difficult to verify reimbursement accuracy or anticipate margin impact before dispensing.
- Spread pricing exposure. In some PBM arrangements, the gap between what a health plan is billed and what the pharmacy receives via MAC generates undisclosed PBM profit — a practice that federal and state regulators have increasingly targeted.
Pharmacies have the right to appeal MAC rates under most state statutes, typically by submitting acquisition-cost documentation within the plan's required timeframe.
Related Terms: Average Wholesale Price (AWP) | Federal Upper Limit (FUL) | NADAC (National Average Drug Acquisition Cost) | Spread Pricing | Pharmacy Benefit Manager (PBM)
