When 28 Wisconsin counties sued several pharmaceutical companies last week, they became among the latest government entities in a wave of litigation accusing the industry of contributing to the prescription opioid and heroin addiction epidemic gripping the country.

From California to New Hampshire, dozens of lawsuits in federal, state and county courts are alleging that Big Pharma inundated the country with painkillers by deceiving doctors and the public about their safety. Many of the cases were brought by plaintiffs lawyers who have teamed up with governments to sue the companies through contingency-fee agreements.

But the recent spate of litigation over the companies' targeted campaigns allegedly claiming that their opioids could be prescribed nonaddictively also has stirred up a significant amount of defense work for Big Law firms. ALM examined court filings in some of these cases to see which firms appear regularly. (The following is by no means a comprehensive list of defense firms that are representing Big Pharma in opioid-marketing litigation.)

OxyContin and Dilaudid manufacturer Purdue Pharma Inc. brought out the big guns: Serving on its legal defense team is Patrick Fitzgerald, a former—and longest-serving—U.S. attorney for the Northern District of Illinois in Chicago and a partner at Skadden, Arps, Slate, Meagher & Flom since 2012. Fitzgerald is arguably best known for his role as the special prosecutor appointed to investigate leaks in the Valerie Plame matter. He also led the high-profile investigation and prosecution of former Illinois Gov. Rod Blagojevich on federal corruption charges. Purdue also regularly turns to Quinn Emanuel Urquhart & Sullivan for its defense work in this area.

Teva Pharmaceuticals USA Inc., maker of Actiq and Fentora, two fentanyl medications, likewise uses Quinn Emanuel for this opioid-related defense work. But the Pennsylvania-based subsidiary of an Israeli company also turns to Philadelphia-based Morgan, Lewis & Bockius, employing lawyers in several of the firm's offices on the various litigation matters.

The main go-to firm for Johnson & Johnson and its subsidiary Janssen Pharmaceuticals Inc., which makes Duragesic and Nucynta, also fentanyl medications, is West Coast-based O'Melveny & Myers, led by partner Charles Lifland. And it's not Lifland's first time defending the drug company over marketing claims. He was part of the litigation team that in 2014 was instrumental in reversing $1.4 billion in civil penalties and attorney fees against J&J and a subsidiary over marketing of the antipsychotic medication Risperdal. According to Lifland's firm bio, leading technology, energy, pharmaceutical and medical device companies, including Exxon Mobil Corp., J&J and Merck & Co. Inc., turn to the Los Angeles-based partner for their most important litigation matters.

For Endo Pharmaceuticals Inc., maker of Opana and Percocet, it's generally Arnold & Porter Kaye Scholer all the time. Attorney Anthony Boccanfuso and partner Ingo Sprie, both in the firm's New York office, are handling some of the more recently filed suits, including one brought by the state of Ohio in May, as well as dozens filed on behalf of various New York counties over the past few months.

A relatively new twist in the opioid-marketing litigation is to go after the drug distributors, namely Amerisource Bergen Corp., Cardinal Health and McKesson Corp., rather than the manufacturers. The first government entity to do so was the Cherokee Nation, which alleged in an April lawsuit that the companies violated tribal and federal laws by turning a blind eye as prescription painkillers flooded the streets. The drug distributing giants have turned to various firms in Tulsa, Oklahoma, including Crowe & Dunlevy for Amerisource Bergen; Doerner, Saunders, Daniel & Anderson for McKesson; and Hall Estill and Norman Wohlgemuth Chandler Jeter Barnett & Ray for Cardinal Health. But Cardinal Health didn't keep it all in Oklahoma. Also listed as counsel on the company's June 12 motion to dismiss are three attorneys from the Washington, D.C., office of Williams & Connolly.