Opioid MDL Amendment Fight: Rule 15/16 Showdown at the Sixth Circuit
On July 27, 2026, U.S. District Judge Dan Aaron Polster, who has presided over the National Prescription Opiate Litigation in the Northern District of Ohio since it was centralized in 2017, issued an order permitting roughly 800 plaintiffs to amend their complaints to add pharmacy benefit managers OptumRx and Express Scripts as defendants. Both companies process prescription-drug claims for insurers and, according to plaintiffs, played a role in facilitating the oversupply of prescription opioids. Both deny wrongdoing.25
The amendments came years after the deadlines most litigants in the MDL had operated under for adding new claims and defendants. On August 27, 2026, OptumRx and Express Scripts petitioned the Sixth Circuit for a writ of mandamus, an extraordinary form of appellate relief, reserved for cases involving a clear abuse of discretion or a judicial usurpation of power asking the court to strike the amendments. The Sixth Circuit responded on September 1, ordering the Plaintiffs’ Executive Committee to answer the petition, with further briefing expected in the weeks that follow.26
Notably, the companies are not primarily contesting whether they are liable1. Their petition is about process, as to whether the district court was permitted to evaluate the amendments collectively, as an MDL-wide administrative matter, rather than requiring each of the 800 plaintiffs to individually satisfy the showing that Rules 15 and 16 would otherwise demand.27
Rule 15 and the Preference for Deciding Cases on the Merits
Federal Rule of Civil Procedure 15 reflects one of the more forgiving instincts in federal practice that courts are instructed to grant leave to amend a pleading ‘when justice so requires,’ rather than letting a case turn on a technical pleading defect. Under Rule 15(a)(2), once a party has used up its right to amend as a matter of course, it needs either the opposing party’s consent or the court’s permission but that permission is supposed to be readily available absent a good reason to withhold it, such as undue delay, bad faith, or prejudice to the opposing party.28
Rule 16 and the Discipline of Scheduling Orders
Rule 15 does not operate in a vacuum, though. Once a court has entered a scheduling order and MDL courts routinely do, setting deadlines for amended pleadings, discovery cutoffs, and dispositive motions, Rule 16(b)(4) takes over. A scheduling order ‘may be modified only for good cause and with the judge’s consent’. That is a materially different, and generally harder standard than Rule 15’s ‘justice so requires’.29
Practically, that means a plaintiff seeking to amend a complaint after a court-set deadline typically has to clear two hurdles rather than one, which is firstly, to demonstrate good cause under Rule 16 for missing the deadline in the first place, and only then get the benefit of Rule 15’s liberal amendment standard. Courts across the country have held that a plaintiff cannot simply invoke Rule 15’s forgiving standard to bypass Rule 16’s good-cause requirement. The scheduling order has to be dealt with on its own terms.
That is where OptumRx and Express Scripts are focusing their petition. They argue that the district court’s order did not walk through that two-step analysis for each of the 800 plaintiffs. It addressed the timing issue collectively, as a function of managing the MDL efficiently, rather than requiring individualized showings of good cause.
Not the Sixth Circuit’s First Look at This Exact Problem
This is not a novel question for the Sixth Circuit in this particular MDL. In April 2020, the appellate court granted a writ of mandamus after Judge Polster allowed two Ohio counties, Cuyahoga and Summit to add claims to their complaints after the relevant deadline had passed. The Sixth Circuit held at the time that the district court’s stated rationale that individualized review of every amendment would consume ‘colossal resources’ and undercut the efficiency the MDL was designed to create. This did not excuse compliance with Rule 16(b)’s good-cause requirement. The court’s message then was direct as to whether MDL courts have broad authority to create efficiencies, but that authority operates within the Federal Rules, not around them.30
OptumRx and Express Scripts are effectively arguing that Judge Polster has repeated the same procedural shortcut the Sixth Circuit already rejected once, with this time across a larger group of plaintiffs and a different set of defendants, but with the same underlying defect.
Why Plaintiff-Side Practitioners Should Watch Closely
For firms handling mass tort and MDL work, this case touches a live practical question as to how much can new evidence discovered mid-litigation actually be used to add a defendant, once a scheduling order has closed the amendment window.31
Multidistrict litigation now makes up a substantial majority of the federal civil caseload, with recent federal judiciary data put the figure well above 50%, with some assessments running into the mid-60s to 70% range of all pending federal civil cases. That scale means the procedural rule that emerges from this dispute won’t stay contained to opioid litigation. It will shape practice in the product-liability, pharmaceutical, medical-device, and toxic-tort MDLs that make up the bulk of that docket including several of the dockets firms in this space are actively litigating right now.32
The bottom line is that mandamus relief is intentionally hard to obtain. The Sixth Circuit reserves it for genuinely extraordinary circumstances, not ordinary disagreements about case management. This cuts against OptumRx and Express Scripts succeeding outright. But this court has already granted mandamus once in this exact MDL, on a closely related question, which makes the current petition harder to dismiss as a long shot. Whatever the Sixth Circuit decides, the underlying principle is one every mass tort practitioner already knows in the abstract and is now being tested at scale that an MDL’s size does not change what the Federal Rules require. It just makes compliance with them a great deal more expensive to get right.