Key Takeaways

  • The Sixth Circuit granted mandamus and vacated a sweeping order in the national opioid MDL that had allowed plaintiffs to amend their complaints to assert claims against pharmacy benefit managers nearly two years after the deadline.
  • According to the Sixth Circuit’s decision, MDL efficiency concerns cannot displace the individualized inquiries required by the Federal Rules. The decision provides further support for challenging late amendments in MDLs and other coordinated proceedings and for holding plaintiffs to their procedural obligations and case-specific records.

In its unanimous October 2, 2026, order, a three-judge panel held that U.S. District Judge Dan Aaron Polster “clearly abused” his discretion under Federal Rule of Civil Procedure 16 by permitting 800 plaintiffs to amend their complaints to add pharmacy benefit managers (“PBMs”) many years into the national opioid MDL, and long after the deadline to amend had expired. The PBMs’ mandamus petition described the amendments as creating “a tenfold increase in the number of plaintiffs” naming the PBMs.

The panel granted mandamus relief, holding that the MDL court failed to properly apply Rule 16’s requirement of a showing of “good cause” to modify a case scheduling order. By allowing omnibus motions to amend and granting leave to amend across all cases based on broad conclusions about plaintiffs’ knowledge, the MDL court failed to “examin[e] each plaintiff’s awareness of their claims against the PBMs or their diligence in pursuing those claims.”

Separately, the panel held that the MDL court violated Federal Rule of Civil Procedure 15 by granting leave to amend without ensuring the PBMs had adequate notice of each plaintiff’s proposed amendments. Judge Polster’s “notice-in-the-aggregate approach” effectively required the PBMs to “stitch together” the allegations in one city’s complaint against the PBMs with those in each individual plaintiff’s complaint. The panel emphasized that “efficiency cannot replace the individualized inquiry that Rule 15 requires.” 

In his response to the PBMs' mandamus petition, Judge Polster expressed concern that disallowing the requested amendments would scatter litigation across jurisdictions, generating “a flood of subpoena[s], uncoordinated discovery deadlines, conflicting party requests, contradictory court rulings, and ‘pretrial chaos.’” The panel nevertheless vacated the MDL court’s order and directed the court “to conduct an individualized diligence analysis under Rule 16” on remand.