More U.S. companies are looking to trim their tax bills by combining operations with foreign businesses in a trend that may eventually cost the federal government billions of dollars in revenue.

Generic drugmaker Mylan Inc. said Monday it will become part of a new company organized in the Netherlands in a $5.3 billion deal to acquire some of Abbott Laboratories’ generic-drugs business. The deal is expected to lower Mylan’s tax rate to about 20 percent to 21 percent in the first full year and to the high teens after that.

The deal by the company, based in Canonsburg, Pennsylvania, follows a path explored by several other U.S. drugmakers in recent months. AbbVie Inc. has entered into talks with Shire Plc. over a roughly $53.68 billion deal that would lead to a lower tax rate and a company organized on the British island of Jersey.

But drugmakers aren’t the only companies looking overseas for better tax deals.

Last month, U.S. medical device maker Medtronic Inc. said that it had agreed to buy Ireland-based competitor Covidien for $42.9 billion in cash and stock. The combined company would have executive offices in Ireland, which has a 12.5 percent corporate income tax rate. And drugstore chain Walgreen Co. – which bills itself as “America’s premier pharmacy” – also is considering a similar move with Swiss health and beauty retailer Alliance Boots.

These tax-lowering overseas deals, which are called inversions, have raised concerns among some U.S. lawmakers over the potential for lost tax revenue. But business experts say U.S. companies that find the right deal have to consider inversions because of the heavy tax burden they face back home.

At 35 percent, the United States has the highest corporate income tax rate in the industrialized world. By contrast, the European Union has an average tax rate of 21 percent, said Donald Goldman, a professor at Arizona State University’s W.P. Carey School of Business.

In addition to the higher rate, the United States also taxes the income that companies earn overseas once they bring it back home. The tax is the difference between the rate the company paid where it earned the income and the U.S. rate.

“We tax income whereever it is earned around the world once you bring it back home, and almost nobody else does that,” Goldman said.

In addition to lowering a company’s tax rate, inversions also can help a company reduce its U.S. tax liability through a process known as earnings stripping. Essentially, the U.S. business takes on debt to fund a dividend for its foreign operations and deducts interest payments on that debt.

Tax lawyer Bret Wells said companies consider an inversion only if they can put together a good deal that will help grow their business. The inversion is really a secondary benefit, but also a way for corporations to “vote with their feet.”

“When I can see that the other guy, my competitor, can reduce their tax bill, I want to look like them,” said Wells, an assistant law professor at the University of Houston.

President Obama has proposed raising the threshold for inversions on foreign entity ownership to 50 percent, with the goal of making them less attractive.

But Wells, the tax lawyer, says more comprehensive tax reform is needed.

In the meantime, experts say companies will continue to consider inversions.