(Reuters) -The three largest U.S. drug distributors have agreed to pay $300 million to resolve claims by health insurers and benefit plans that they helped fuel the deadly U.S. opioid epidemic, according to court papers filed on Friday.

The proposed class action settlement with McKesson Corp ( MCK ), Cencora Inc ( COR ) and Cardinal Health Inc ( CAH ) was disclosed in a filing in federal court in Cleveland, Ohio, and requires a judge's approval.

Those companies had previously agreed to pay $21 billion to resolve claims by state and local governments accusing them of having lax controls that allowed massive amounts of addictive painkillers to be diverted into illegal channels.

Paul Geller, a lawyer for the plaintiffs, said in a statement that Friday's deal covered third-party payers like union funds that "largely paid for the overprescribed and overmarketed pills and for the treatment required when their plan beneficiaries inevitably suffered opioid use disorder."

The distributors did not admit wrongdoing as part of the settlement. The $300 million will be paid 38.1% by McKesson, 30.9% by Cardinal and 31% by Cencora ( COR ), which was previously known as AmerisourceBergen.

The case was among thousands that have been filed seeking to hold various drug makers, distributors and pharmacies responsible for a drug addiction epidemic that resulted in hundreds of thousands of overdose deaths nationally over the last two decades.

The litigation has resulted in more than $50 billion in settlements, largely with states and local government.