The American Antitrust Institute joined the list of industry voices opposing the merger between CVS and Aetna. AAI sent a letter this week requesting the Department of Justice block the merger, citing concerns that should this deal and the other large merger in the industry (Express Scripts and Signa) go through, competition would all but cease.

"Assuming both mergers move forward, the three large integrated PBM-insurer systems (i.e., CVS-Aetna, Express Scripts-Cigna and Optum Rx-United Healthcare) that would dominate the markets would have weak, if any, incentives to compete," AAI said in its letter. "This would effectively lock out competition by stand-alone PBMs, insurers and other market participants.”

CVS-Aetna’s general counsel pledged in a congressional hearing that the merger would not increase costs and restrictions, but not everyone thinks this will hold up.

"Genuine risks to competition won't be fixed by pledges of good behavior,” Consumers Union Senior Policy Counsel George Slover told FierceHealthcare.

The American Medical Association has also expressed skepticism about these mergers.

"Close scrutiny is needed to determine if the ramifications of this massive merger will threaten the benefits of competition, including increased access and choice, lower prices and higher quality care for patients," AMA President David Barbe told FierceHealthcare.

CVS and Aetna maintain that the $69B merger deal would not hurt competition and that together they can increase community-based care.