Merck and impossibility preemption | The American Association For Justice Archive

Merck and impossibility preemption

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April 2019 - Matthew Wessler


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When patients injured by FDA-approved drugs sue manufacturers under state law for failing to warn of dangerous side effects, manufacturers often raise “impossibility preemption” as a defense, contending that federal regulations would have forbidden the warning that plaintiffs allege state law required. If successful, this defense could allow manufacturers to avoid liability for making and selling drugs that have injured patients.

Three times over the last decade—in Mutual Pharmaceutical Co., Inc. v. Bartlett,1PLIVA, Inc. v. Mensing,2 and Wyeth v. Levine3—the U.S. Supreme Court affirmed that state law failure-to-warn claims are not preempted under the Federal Food, Drug, and Cosmetic Act4 when federal law permits a drug manufacturer “‘to unilaterally strengthen its warning’ without prior FDA approval.”5 The Court agreed to revisit impossibility preemption to potentially clarify how to decide impossibility preemption questions and who should resolve them when it granted certiorari in Merck Sharp & Dohme Corp. v. Albrecht.6

In Wyeth, the Court held that a drug manufacturer claiming impossibility preemption must produce “clear evidence” that the FDA would have prohibited an additional warning.7 Yet despite this standard, drug companies, including Merck in this case, continue to push for an expansive interpretation of impossibility preemption that would preempt state laws based on even a hypothetical conflict with federal law.

In Merck, the Third Circuit reversed summary judgment for the defense and remanded the case for a jury, not a judge, to decide.8 The court held that Merck was unable to satisfy Wyeth’s clear evidence standard because the key question—whether the FDA would have prohibited an additional fracture warning on Merck’s osteoporosis drug Fosamax—turned on disputed factual questions about “what would have happened.”9

Merck argued to the Supreme Court that, contrary to the plaintiffs’ claim, it could not have added language warning Fosamax users about the risk of serious atypical femoral fractures (AFF) because the FDA had previously rejected a proposed warning on stress fractures and likely would reject another one. But as AAJ argued in its amicus brief, under Wyeth, a manufacturer claiming impossibility preemption should be required to show that the FDA rejected a proposed warning—not that it would hypothetically have done so.10

During oral arguments in January, several justices focused on the potential consequences of a ruling favoring the drugmaker. Justice Neil Gorsuch asked whether a ruling for Merck could encourage manufacturers to “deliberately inartfully” draft warnings “reasonably calculated” to be refused by the FDA.11 Doing this, he suggested, might provide unjustified cover to drug manufacturers for later deciding not to add a new warning. Justice Elena Kagan observed that the “whole question boils down” to whether Merck’s initial proposal and the FDA’s response were “talking about the same things” with both understanding “stress fracture” to include AFF.12

But a majority of the justices seemed skeptical that the record on what the FDA would have done had Merck ­proposed a new warning was so uncertain­. A ­lawyer appearing on the U.S. government’s behalf supported Merck’s position arguing that Merck’s initial warning on “stress fractures” included “any fracture that was caused without external trauma”—a warning that covered AFF.13 

Justice Stephen Breyer indicated that the FDA’s actions were sufficiently clear. In his view, had Merck proposed a new AFF-specific warning, the FDA would have rejected it because the agency “didn’t know enough about [the specific risks associated with AFF] and, therefore Merck couldn’t have done it.”14 And Chief Justice John Roberts observed that if “the question is what the FDA understood,” then the government’s view that a subsequent proposal from Merck would have been rejected should be controlling.15

Justice Kagan, for example, suggested that if the FDA was alerted to a problem but didn’t “know whether a change” in the label was appropriate and so decided to “continue to study” it, then the manufacturer likely shouldn’t be required to change the label.16 Only a few justices seemed to agree with plaintiff counsel that the proper legal test should turn on whether there was “official action by the FDA that prevented Merck from changing its label” or that a jury “should decide whether the FDA would have approved” the warning.17

Given the record-intensive nature of this issue and the justices’ keen focus during oral arguments on the case’s specific facts, the Court may be headed for a decision that, in Justice Kagan’s words, makes this a “much smaller case.”18 The Court may avoid deciding once and for all how impossibility preemption works in the drug approval context, opting instead to focus on the specific communications between the FDA and Merck and the science known at the time to resolve the availability of the preemption defense here. A decision is expected by June.

Matthew Wessler is a principal at Gupta Wessler in Washington, D.C., and can be reached at


  1. 570 U.S. 472 (2013).
  2. 564 U.S. 604 (2011).
  3. 555 U.S. 555 (2009).
  4. 21 U.S.C. §§301 et seq. (2018). 
  5. Mensing, 564 U.S. at 624 (citing Wyeth, 555 U.S. at 573); see also Bartlett, 570 U.S. at 490.
  6. No. 17-290 (U.S. oral arg. Jan. 7, 2019). 
  7. Wyeth, 555 U.S. at 571. 
  8. In re Fosamax (Alendronate Sodium) Prods. Liab. Litig., 852 F.3d 268, 302 (3d Cir. 2017). 
  9. Id. at 289. 
  10. Mr. Wessler coauthored the amicus brief. To see all the amicus briefs that AAJ has filed since January 2014, visit
  11. Oral Arg. Tr. 13:13–14, Merck Sharpe & Dohme Corp. v. Albrecht (No. 17-290) (U.S. Jan. 7, 2019),
  12. Id. at 6:9, 6:11–12. 
  13. Id. at 22:24–25. 
  14. Id. at 41:17–19. 
  15. Id. at 43:12–13, 44:6–17. 
  16. Id. at 50:10–12. 
  17. Id. at 58:16–18, 59:10–11. 
  18. Id. at 6:1.