What a PBM actually does
A pharmacy benefit manager (PBM) administers the drug side of a health plan: it builds the formulary (which drugs are covered on which tiers), contracts the pharmacy network, processes claims at the register in real time, negotiates rebates with drug manufacturers, and increasingly owns the specialty and mail-order pharmacies it steers members toward.
Three PBMs process the large majority of U.S. prescriptions, and each sits inside a vertically integrated healthcare conglomerate alongside an insurer and pharmacies. That integration is why PBM contracts deserve the same scrutiny a self-funded employer applies to any major vendor: the entity setting the prices has affiliates on multiple sides of the transaction.
How PBMs make money — the three mechanisms to understand
- Spread pricing. The PBM charges the plan one price for a claim and reimburses the pharmacy a lower one, keeping the difference. The spread is invisible unless the contract requires pass-through pricing.
- Rebate retention. Manufacturers pay rebates for formulary placement — often enormous on brand drugs. Contracts differ on how much reaches the plan ("100% of rebates" definitions hide as much as they promise: rebates, admin fees, and "other manufacturer revenue" can be defined as different pots).
- Affiliated-pharmacy steering. Mandating the PBM's own specialty or mail pharmacy concentrates the plan's most expensive claims where the PBM sets the price.
None of this makes PBMs useless — real formulary and network management has value — but it makes the contract the product. Independent and "transparent" pass-through PBMs compete precisely on these terms.
What plan sponsors should do about it
The fiduciary era has put pharmacy contracts squarely in scope, and the working checklist is consistent:
- Get the data. CAA transparency rules strengthened sponsors' right to their own claims; pair pharmacy data with the medical side in your claims analysis.
- Audit the contract independently — spread, rebate definitions, affiliated-pharmacy terms, and termination rights. Specialist pharmacy consultants routinely find material gaps.
- Market-check periodically, including transparent/pass-through PBMs sized for your book.
- Watch specialty utilization management — the handful of members on specialty drugs usually drive most pharmacy spend; site-of-care and biosimilar strategies matter more than copay tweaks.
Pharmacy is one pillar of the broader cost containment picture — the medical side's equivalent lever is keeping avoidable episodes out of facilities.