While the U.S. Department of Justice may not have plans to challenge the $69 billion mega-merger of CVS and Aetna, patients and physicians should do so at every turn. The acquisition of the country's third largest insurer by the nation's largest pharmacy benefit manager could not only increase health-care costs, but restrict access to care for millions of insured Americans.

CVS and Aetna claim their union — which will combine a health insurance payer, pharmacy benefit manager (PBM), and national retail pharmacy network under one roof — could streamline inefficiencies, reduce the price of prescription drugs and cut down on doctor and emergency room visits by allowing patients to receive basic clinical care at walk-in CVS MinuteClinics.

The merger may boost profits for both companies but could severely limit patient choice when it comes to seeing a doctor or filling a prescription, and will almost certainly increase health-care costs by providing even less transparency into the already murky world of prescription drug prices.

For example, Aetna could limit choice by requiring patients to visit a CVS MinuteClinic before, or instead of, seeing their own doctor, even though regular, seemingly routine visits to a primary care physician have been shown to be important for patients, especially for needed preventative care. Aetna could also require patients to fill their prescriptions only at CVS pharmacies, severely limiting patient options for where and how they get their medications. Requiring Aetna customers to use CVS pharmacies could also sound the death knell for independent pharmacies and cause drug prices to rise, particularly in underserved communities.

With even less price transparency, patients can expect reduced choices. Insurer and PBM confidentiality agreements already make it virtually impossible to know exactly what prescription drugs actually cost because payers and PBMs negotiate prices behind closed doors. These secret agreements and drug rebate "kickbacks" are largely responsible for higher drug prices in the first place, as several class-action lawsuits have alleged. If competitors like Aetna and CVS are allowed to merge, you can be sure price negotiations would become even more opaque and prescriptions even more expensive.

Both CVS and Aetna claim that housing a payer, retailer, and PBM under one umbrella would make managed care cheaper and more efficient. But, even if consolidation improved efficiency, it is unlikely that any cost savings would be passed to patients. Aetna already has a history of prioritizing profits over patients by deliberately blocking access to care. A former Aetna medical director recently admitted that he never looked at patients' medical records when deciding to approve or deny claims, a revelation that resulted in multiple states launching investigations into Aetna's claims review process. A pediatric physician group recently filed suit against the insurer for "improperly interfering with medical care," alleging that Aetna executives "do not concern themselves with the actual care being delivered," even for "justified and life-saving care," but are solely "motivated by a desire for ever-increasing profits."

The growing trend of restricting patients' access to care is not limited to Aetna. A recent report found that up to 53 million Americans may lack access to prescribed treatments for chronic illnesses because their insurer would not cover the cost.

What should worry insured Americans even more is that a CVS-Aetna merger could set off a wave of other acquisitions, further consolidating the health-care sector under the control of a few powerful companies. Insurance giant Cigna already has an agreement to acquire PBM Express Scripts, and there are rumors of a possible Walmart-Humana acquisition. According to the American Medical Association, such mergers will further restrict access, reduce quality, and make care less affordable, even while increasing premiums and expanding the out-of-pocket costs for prescription drugs.

Among those urging the DOJ to block the deal is California's Insurance Commissioner, who argued the sheer size of the merger "will likely lead to increased prices and decreased quality" and "have significant anti-competitive impacts on American consumers, health care and health insurance markets."

Health care is getting too far out of reach for most Americans, even with insurance. Reforms must start with price transparency and removing barriers to care for patients, not looking the other way when the industry's largest and most powerful gatekeepers join forces to boost their profits and market share. Lawmakers and the Department of Justice must intervene to prevent these so-called vertical health-care mergers and prevent even more consolidation that would increase costs, reduce choice and limit access to care for millions of insured Americans.

Theresa Rohr-Kirchgraber, MD, is the past president of the American Medical Women's Association and a founding member of the Doctor-Patient Rights Project.