A Pfizer-Allergan deal is likely to fuel critics’ concerns that consumers would pay even more for drugs as competition declines among manufacturers, insurers and retailers.

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After weeks of talks, Pfizer and Allergan are set to approve a blockbuster merger worth $150 billion.

The companies’ boards of directors were reportedly expected to approve the deal Sunday, with details probably announced Monday, according to The Wall Street Journal. If completed, it would cap a remarkable consolidation wave roiling the U.S. health-care industry and create the world’s biggest drugmaker by sales.

As of Friday’s close, Pfizer had a market cap of $199 billion; Allergan was at $123 billion.

A Pfizer-Allergan deal is likely to fuel critics’ concerns that consumers would pay even more for drugs as competition declines among manufacturers, insurers and retailers.

The deal is structured so that Ireland-based Allergan is technically buying its much larger partner, a move that may make it easier for the company to locate its tax address in a lower-cost country.

The agreement is designed to reduce tax payments and bring together the makers of Viagra and Botox.

The U.S. Treasury Department has increasingly targeted such strategies, most recently announcing new guidance on how it will value assets owned by U.S. companies that undertake such so-called “inversions.”

The U.S. has the highest tax rate for businesses in the world, at 35 percent, and is one of the only countries to tax corporate profits wherever they are earned.

Previous moves by the Treasury have derailed other proposed inversions, including AbbVie’s plan to buy Ireland’s Shire for an estimated $52 billion.

The deal would place the companies squarely in a presidential-election debate over efforts by U.S. companies to obtain lower tax rates by using mergers to move their headquarters abroad.

The final terms of the deal include 11.3 Pfizer shares for every Allergan share, the Journal, citing unidentified sources, said. The deal also contains a small cash component, the paper reported.

It said Pfizer Chief Executive Ian Read would lead the company and that Allergan CEO Brent Saunders would be second-in-command.

A month ago, Allergan, which has a sizable operation in Irvine, Calif., said it was approached by New York-based Pfizer but cautioned that there was “no certainty” that the “friendly” discussions would lead to a merger. Pfizer confirmed the talks.

A deal would cap a merger spree throughout the U.S. health-care industry this year, which already has seen a record $448 billion in announced deals, according to Dealogic, which tracks the market.

Health-care companies of all stripes are joining forces to reposition themselves as various market and government forces, notably the Affordable Care Act, have complicated the growth outlook for the companies’ revenues and profits.

For instance, two of the nation’s three largest drugstore chains, Walgreens and Rite Aid, announced a $9.4 billion merger in October. In July, Anthem reached a $54 billion deal to buy rival Cigna to create the largest U.S. health-insurance company.

This new deal would be unprecedented on many levels. It’s the largest so far this year. It’s the largest ever in the pharmaceutical world, eclipsing Pfizer’s purchase of Warner-Lambert in 2000 for $116 billion.

An agreement may also facilitate the widely discussed potential for Pfizer to reconfigure itself by splitting the newly enlarged company into two: one focused on drug development, the other on selling older medications.