In announcing the lawsuit, Ohio Attorney General DeWine argued the drugmakers’ deception continued “despite the warnings in the small print of their very own drug labels and package inserts which clearly contradict their marketing.”

“You can give a great warning but undercut it, and that can go to the fraud point,” Tobias said.

In September, the federal judge overseeing Chicago’s opioid lawsuit allowed the case to proceed after finding the city alleged sufficient facts to back its claim that the companies deceived healthcare providers.

Fraudulent marketing was also at issue a decade ago when Purdue paid more than $600 million and pleaded guilty to misbranding the opioid drug OxyContin by falsely touting it as less addictive than rival products.

Along with their arguments based on FDA approval, the drug companies are also taking aim at state and local governments’ use of private plaintiffs’ lawyers to bring opioid lawsuits in exchange for a percentage of any settlement or judgment.

Five law firms are representing Ohio on a contingency-fee basis. Drugmakers have argued their constitutional due process rights are violated when profit-seeking private lawyers, as opposed to public servants, pursue government cases seeking large damages.

The companies scored a victory in 2016 when a judge invalidated one such agreement between former New Hampshire Attorney General Joseph Foster and the law firm Cohen Milstein Sellers & Toll.

Now on appeal to the New Hampshire Supreme Court, the ruling effectively blocked the state from filing a lawsuit. A similar bid is underway to invalidate a contingency fee deal between the law firm Simmons Hanly Conroy and New York’s Suffolk County.

Paul Hanly, of Simmons Hanly Conroy, said the drug companies were making a “completely frivolous argument” that would not deter opioid litigation. He is representing three other New York counties in opioid lawsuits and preparing to bring lawsuits on behalf of several more. “What we’re seeing is a feeding frenzy as plaintiffs’ lawyers are looking around and seeing this high-profile litigation and are clamoring to get in,” Hanly said.