Judge Dan Polster is overseeing the consolidated lawsuits in a case in federal court in Cleveland.
The complaints allege drug manufacturers and drug distributors bear responsibility for the deadly overdose epidemic and for not doing enough to stop it.
Polster is trying to hammer out a settlement between the industry and communities that have filed complaints.
Polster allowed 12 more lawsuits into the case on Tuesday, bringing the total to more than 320.
The new cases include lawsuits brought by the city of Lebanon, Ohio; Marion County, Alabama; Candler County, Georgia; Onondaga County, New York; and Skagit County in Washington state.