Major drugstore chains — which face an October trial in the mammoth federal opioid litigation — have sued doctors across northeast Ohio, claiming that physicians are the real culprits in the nation’s deadly drug epidemic.

CVS, Walgreen Co., Walmart, Rite Aid and other major pharmacy chains said opioid prescribers bear responsibility for the prescription narcotic crisis, but unlike the drugstores, have not been sued by Cuyahoga and Summit counties. In legal papers filed Monday, they contended that doctors and other prescribers should have to pay some of the penalty if the drugstore chains are found liable at trial.

The doctors in the nearly identical lawsuits are unnamed, identified only as “John and Jane Does 1-500.” The drugstores said they would name them if it became apparent during legal proceedings who they are.

“In a misguided hunt for deep pockets, without regard to actual fault or liability, plaintiff has elected not to sue any of these other parties,” attorneys for drugstore chains said in the papers.

Drug manufacturers and distributors agreed or were ordered to pay hundreds of millions of dollars in settlements and one court verdict reached in state and federal courts last year. But the big pharmacy chains have not been held liable so far.

More than 2,500 cities, counties, Native American tribes and other groups have filed federal lawsuits against companies throughout the drug industry over the epidemic, which has resulted in the overdose deaths of more than 400,000 people over the past two decades. Those cases have been consolidated in a sprawling “multidistrict litigation” before U.S. District Judge Dan Aaron Polster in Cleveland.

Polster has been urging all sides in the complex legal battle to reach a settlement. At the same time, he has designated the two northeast Ohio counties as “bellwether” plaintiffs, whose litigation would serve as a test case of how dozens of other parties might fare if their lawsuits come to trial.

In the first of those trials, mainly against companies that distribute drugs to pharmacies, hospitals and elsewhere, a last-minute settlement was reached in October between the counties and five companies. Walgreen Co., the only pharmacy chain named as a defendant in that case, did not participate in the deal.

In 2018, Cuyahoga and Summit counties sued the major drug chains, alleging they failed to halt diversion of prescription narcotics to the black market as they distributed drugs to their own stores. But Polster allowed them to amend their accusations to include failures by pharmacists in dispensing the drugs, as well. That prompted the new lawsuit.

“This complaint is required to respond to the unsubstantiated allegations by plaintiffs that pharmacists should not have filled prescriptions, written by doctors, for FDA-approved opioid medications,” Phil Caruso, a spokesman for Walgreen Co., said in an email Tuesday. “We strongly believe that the overwhelming majority of prescriptions dispensed were properly prescribed by doctors to meet the legitimate needs of their patients.”

On Wednesday, the lead attorneys for the municipalities suing the drug industry said in a statement that many groups have some responsibility for the drug epidemic. But, they said, “the origins of the opioid crisis and the fuel that spread the epidemic can be traced back to the behavior and practices of corporations in the drug supply chain. Without widespread wrongdoing by the opioid industry—including pharmacies—we would not be in the place we are today.”

Only doctors and some physician assistants and nurse practitioners can prescribe narcotics, and the drug industry has long attempted to pin much of the blame for the epidemic on them. But federal regulations assign pharmacists a “corresponding responsibility” to ensure that prescriptions are legitimate and help prevent diversion of painkillers to illicit users and dealers.

Despite that regulation, the pharmacy chains are trying to argue in the new legal papers that “we’re not gatekeepers, we’re just toll collectors,” said Elizabeth Chamblee Burch, a University of Georgia law professor who has followed the national opioid litigation closely. She said dragging doctors into the fray also could help the chains’ legal strategy by making the case more complicated.

“It seems to both try to pass the buck onto these third-party doctors, and put the onus on the plaintiffs to identify them,” she said.

Alexandra Lahav, a professor at the University of Connecticut School of Law who also follows the case, said the companies may be signaling to Polster that if pharmacists are going to be held responsible for their dispensing activity, they will want to examine the prescribing habits of doctors across the two counties — a seemingly huge task.

“This is an illustration of how complex and maybe impossible it may be to prove the underlying claim that Cuyahoga County is trying to prove against these drugstores,” she said. “Are we going to question every time we dispensed a drug over a 20-year period?”

In the lawsuits against doctors in the two counties, the chains noted the counties did not sue independent drugstores, pill mills, Internet pharmacies, clinics and other practitioners, though they provided more than 40 percent of the opioids dispensed in Cuyahoga County and more than 60 percent of the opioids dispensed in Summit County.

Nor did the plaintiffs identify a single prescription that was improperly filled, they said. The counties’ case relies more on statistical modeling and government data that they said reveals that millions of doses of narcotics were illegally diverted while the drug industry did little to stop the flow.