What a PBM is
A pharmacy benefit manager, or PBM, is the company that runs the prescription-drug side of a health plan. Health plans, employers, unions, and government programmes like Medicare Part D and Medicaid hire PBMs to manage the drug benefit: deciding which medicines are covered and on what terms (the formulary), assembling the network of pharmacies enrollees can use, negotiating rebates with drug manufacturers, processing the claim each time a prescription is filled, and setting how much each pharmacy is paid. The PBM sits in the middle of the supply chain — between manufacturers, insurers, pharmacies, and patients — so much of what a patient pays at the counter, and what a pharmacy is reimbursed, is set by PBM rules.
A concentrated, integrated market
Three firms dominate. The FTC’s July 2024 staff report found the three largest PBMs — CVS Caremark, Express Scripts, and OptumRx — processed nearly 80% of US prescriptions in 2023, and the six largest handle about 95%. They are also vertically integrated: OptumRx is owned by UnitedHealth, Express Scripts by Cigna, and CVS Caremark by CVS Health (which also owns the insurer Aetna), and each runs its own mail-order and specialty pharmacies. The FTC’s follow-up report (January 2025) found the three largest marked up specialty generic drugs at their affiliated pharmacies by hundreds to thousands of percent, taking more than $7.3 billion above estimated acquisition costs from 2017 to 2022.
Why it matters for pharmacies
Because the PBM sets the reimbursement, several of the disputes this site tracks come back to PBM practices: billing a plan more than the pharmacy is paid (see spread pricing), recovering money from a pharmacy after a claim is paid (see clawbacks and DIR fees), and the state laws that set a reimbursement floor below which a pharmacy cannot be paid. The state tracker records where each state has acted.