In its Opinion dated July 13, 2026, the United States Court of Appeals for the Second Circuit overturned dismissals of Plaintiffs’ failure-to-warn claims under state law relating to acetaminophen, the active ingredient in Tylenol and its generic equivalents. The Plaintiffs are children, parents, and guardians who allege that prenatal ingestion of acetaminophen caused them or their children to develop attention-deficit/hyperactivity disorder (“ADHD”) and/or autism spectrum disorder (“ASD”). The Defendants are the pharmaceutical companies, pharmacies, and retailers involved in the manufacturing, marketing, and/or sale of acetaminophen products.
In one of the two cases on appeal, the Plaintiffs relied on the general causation testimony of five experts—Dr. Andrea Baccarelli, M.D., Ph.D., Dr. Eric Hollander, M.D., Dr. Brandon Pearson, Ph.D., Dr. Robert Cabrera, Ph.D., and Dr. Stan Louie, Pharm.D.—who opined as to a possible causal relationship between prenatal acetaminophen use and ADHD and ASD. The district court excluded the testimony of those five experts and granted summary judgment to the Defendants.
In the other case (which alleged injury solely from ADHD), after the district court’s initial ruling, the Plaintiffs introduced an additional expert, Dr. Roberta Ness, M.D., M.P.H., to testify as to a possible causal relationship between prenatal acetaminophen use and ADHD only. The district court excluded her testimony and granted summary judgment to the Defendants.
Because of the substantial overlap of the issues that the two cases presented, the United States Court of Appeals for the Second Circuit considered both cases together, to consider what qualifies as admissible epidemiological testimony in support of a general causal relationship: “We are not deciding whether there is a general causal relationship between acetaminophen and ADHD and/or ASD. We are also not deciding whether the manufacturers of acetaminophen must warn consumers about any alleged risk posed by such a potential causal relationship. And we are certainly not deciding the approach that policymakers concerned with protecting public health should take to regulating the use of acetaminophen. Rather, we are called upon to decide how closely a trial court may scrutinize a qualified expert’s conclusions when that expert follows methodologies that are generally accepted in their field, and the standard of reliability required for the admission of expert testimony on issues that are the subject of ongoing scientific debate.”
“We conclude that, in Rutledge v. Walgreen Co., the district court exceeded its discretion in excluding the expert testimony of Drs. Baccarelli, Hollander, and Pearson. Those concededly qualified experts offered opinions that comport with methodologies applied by other scientists in their fields, and constitute acceptable interpretations of scientific evidence where scientists may, and in fact do, disagree on the ultimate answer to the causal question that they are assessing. The district court did not, however, abuse its discretion in excluding the testimony of Drs. Cabrera and Louie. The district court was entitled to conclude that Cabrera’s opinion was unreliable because it did not weigh or properly synthesize the factors under the so-called Bradford Hill methodology that he employed. And the district court was similarly entitled to conclude that Louie’s opinion did not reliably address the dose and duration exposure threshold for risk of ADHD and ASD because he failed to explain how he extrapolated from the studies he analyzed to reach his final conclusion. We therefore vacate and remand the district court’s judgment in Rutledge.”
“In Phippen, Plaintiffs-Appellants offered Ness as an expert only after the district court’s exclusion of Baccarelli, Hollander, Pearson, Cabrera, and Louie. With the admission of expert testimony from Baccarelli, Hollander, and Pearson, or for other reasons discussed below, it may be that Plaintiffs-Appellants would no longer seek to offer Ness’s testimony. We therefore vacate the district court’s judgment in Phippen, and remand for such further proceedings as the district court finds appropriate, consistent with this opinion.”
“Finally, Defendants-Appellees argue that in both Rutledge and Phippen we should affirm the district court’s judgment on the alternative ground that federal drug labeling law preempts Plaintiffs-Appellants’ failure-to-warn claims. The district court rejected that argument at the pleading stage. Here, the district court did not err. Federal regulations require acetaminophen manufacturers to display verbatim a general pregnancy warning, but they do not prohibit supplemental, specific warnings against plausible risks.”
Source Rutledge v. Walgreen Co.; Phippen v. Walgreen Co., 24-916(L); 24-2594.
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