"The combination of CVS and Aetna creates an enormous market force that we haven't seen before, straddling more market sectors and creating new and potentially far-reaching profit-maximizing incentives to undermine competition", Slover said in a statement.
CVS has said the deal will enable a variety of new medical services to be brought into its stores, part of its shift from corner pharmacy chain to a hub for health care with thousands of locations around the country.
The approval comes just a few weeks after the US signed off on another deal combining a big health insurer with a pharmacy-benefits manager - Cigna Corp.'s $54 billion takeover of Express Scripts Holding Co. CVS first announced plans to buy Aetna last December.
The deal is aimed at simplifying the healthcare experience for consumers demanding change. The merger, which combines the largest U.S. retail pharmacy chain and the third largest health insurer, represents a paradigm shift toward major consolidation in the industry that could impact patient access and cost of care.
"The divestitures required here allow for the creation of an integrated pharmacy and health benefits company that has the potential to generate benefits by improving the quality and lowering the costs of the healthcare services that American consumers can obtain". But in trying to head off the worst cases, CVS and Aetna are aiming to become a part of the nation's social fabric, using the local retail pharmacy as both a window into people's lives beyond the doctor's office and assuming the role of a health-care assistant.
Aetna shares were up 1.3 percent to $206.36 at 12:01 p.m.in NY.
CVS Health has characterized the merger as a way to serve customers better, noting that 70 percent of Americans live within three miles of one of its pharmacies.
Although mergers such as the CVS-Aetna deal offer the promise of potential cost-savings and patient benefits, health advocacy groups have raised concerns about the long-term impact on pharmacies and patients.
Merlo said in September that the combined Company will have more data, giving CVS a more complete picture of someone's health.
Consolidation has risen across health care among hospitals, drugmakers and insurers.
An attempt by Aetna to acquire Humana was ultimately blocked previous year by antitrust regulators.
Aetna's agreement to sell its Medicare prescription-drug business, in order to get clearance for the merger with CVS, was part of a settlement reached with the Justice Department and five state attorneys general, including California's. It has held talks with Walmart Inc. for a closer partnership to provide health care to consumers at home and prevent illness. His view is that competition problems arising from so-called vertical deals need to be fixed with asset sales rather than imposing restrictions on how companies operate. DOJ's announcement follows a decision last month by regulators to bless a similar PBM deal involving the insurance company Cigna and Express Scripts.