PBM influence is only growing, American Medical Association report finds

The American Medical Association (AMA) released an analysis on competition and vertical integration in the pharmacy benefit managers (PBMs) market in late September. To no one’s surprise, it found that concentration is on the rise and competition is falling.

The concern, the report found, is that PBMs could cause real antitrust issues.

This isn’t the first time PBMs have come under fire. Critiques especially heightened after the Federal Trade Commission (FTC) released a report in 2024 that found the Big 3 PBMs—CVS’s Caremark, Cigna’s Express Scripts, and UnitedHealth Group’s Optum Rx—manage 79% of prescription drug claims for an estimated 270 million people. In its most recent Q3 earnings, UnitedHealth reported $39.9 billion in quarterly adjusted revenue for Optum Rx. Cigna’s Evernorth Health Services reported $34.5 billion in adjusted Q2 revenue for pharmacy benefit services. CVS’s health service segment, which includes Caremark, reported $51.8 billion in total Q2 revenue.

In case you’ve missed the many headlines on the topic, PBMs are the intermediaries that negotiate drug prices between pharmaceutical manufacturers and health insurance companies. AMA’s analysis suggests that a small number of PBMs are growing their share of the market and that most are vertically integrated—meaning they’re also part of a company that owns a health plan—AMA President Willie Underwood said in a Sept. 29 release. (These types of business practices have been associated with rising drug costs.)

“These trends warrant closer scrutiny, greater transparency, and stronger accountability to ensure PBM markets serve patients rather than reinforce the market power of large healthcare companies,” he said.

Report findings. AMA’s analysis pulled prescription drug plan enrollment data between 2022 and 2024. Here are some key takeaways:

• The four largest PBMs in 2024, based on market share, were Optum Rx (23%), Express Scripts (23%), CVS Caremark (18%), and Prime Therapeutics (11%), which is jointly owned by Blue Cross Blue Shield plans. This is a 75% share of the PBM market, up from 70% in 2022, according to the analysis.
• Express Scripts had the largest market share increase of the four, up from 17% in 2022.
• All of the 10 largest PBMs were also owned by a company that has a health insurance arm.
• CVS Caremark was the largest PBM in 2022, but fell to third place in 2024.

PBM probs. There’s been a decent amount of government pressure on PBMs lately.

Congress passed its first big reform bill back in February. States like Tennessee and Arkansas have been attempting to pass laws since May 2026 and May 2025, respectively, to try to split them up from health insurers. Florida and Louisiana sued PBMs in August over drug pricing inflation accusations. And the FTC released another report in 2025 accusing PBMs of increasing costs on 51 specialty generic drugs, which collectively made them more than $7.3 billion in profit from 2017 to 2022. The AMA even has a TruthinRx campaign that calls for greater drug pricing transparency from PBMs.

Still, the AMA shared concerns in its report that market control and vertical integration aren’t going anywhere, and if left unchecked, could create an antitrust issue.

“The findings in this study highlight whether proposed or consummated mergers among PBMs and between insurers and PBMs should raise antitrust concerns,” the report read. The AMA declined to provide further comment on the antitrust concerns suggested in the report.

When asked for comment, CVS Caremark, Express Scripts, and Prime directed Healthcare Brew to the Pharmaceutical Care Management Association (PCMA), a lobbying group that represents PBMs. Optum didn’t respond to a request for comment.

Greg Lopes, a spokesperson for PCMA, told us via email that “the PBM market remains extremely competitive with diverse options for employers to choose from” and that PBMs are the “most transparent part of the supply chain.”