Cliff Aronson knows something about multitasking. An antitrust partner at Skadden, Arps, Slate, Meagher & Flom LLP, Aronson was successfully defending Express Scripts Inc.'s $28 billion takeover of rival pharmacy benefits manager Medco Health Solutions Inc. before the Federal Trade Commission at the same time he was negotiating with the Department of Justice on behalf of HarperCollins Publishers LLC to settle charges that the company had participated in a conspiracy with other publishers and Apple Inc. to prop up the prices of e-books.

Though lawyers are almost always managing multiple clients, it's still a difficult task, says Aronson, 57. "Juggling is hard, especially since every client is my only client when I am working on their matters." He credits "a terrific group of colleagues" -- both within Skadden and at other firms -- with helping him manage the load.

Aronson's team, along with Medco's lawyers from Dechert LLP, Paul Denis and Mike Cowie, managed to win FTC approval to form the largest pharmacy benefits manager without being ordered to make divestitures or comply with other remedies, despite fierce opposition from pharmacists and drugstore chains.

Aronson attributes their success to anticipating the problems that would trouble the FTC and the decision to address them head-on. Specifically, the legal team offered up a mountain of data to counter opponents' claims that the deal would allow Express Scripts to buy its main competitor. "We did an analysis of the companies' bidding records to demonstrate that there were many others in the market and that our clients weren't each other's closest competitors," Aronson says.

The companies also handed over the raw data supporting the analysis so the FTC could verify the conclusions on its own. The data submission went beyond what the FTC had requested from the companies. "It took time, but it was one of the most important factors in the FTC's decision," Aronson says.

Juggling cases also keeps him in the air a lot: A resident of Rye, N.Y., Aronson works out of Skadden's New York headquarters and is a regular flier on the shuttle to Washington.

"I'm in D.C. a couple times a week," he says. "It's an easy round-trip flight, but I bring a change of clothes in case I get stuck and have to stay over."

Aronson's career started in Washington. After graduating from Georgetown University Law Center in 1980, he was the first new graduate hired in Skadden's Washington office. He moved to the New York office 3-1/2 years later. He has spent his entire career at the firm, forgoing the traditional practice of taking a few years from private practice to work for one of the antitrust agencies. "I've thought about working for the government, but what I do is more fun," he says.