Lawsuits Seek to Link Tylenol Ingredient to Autism, ADHD

Whether those cases grow and move forward—with massive financial sums at stake—could depend on a key issue before a federal judge this week: what scientific claims the plaintiffs can cite in court.

Lawyers have filed about 440 product-liability lawsuits, consolidated in a New York federal court, against manufacturers of Tylenol and generic acetaminophen. The lawsuits argue that drugmakers should have warned pregnant women that taking the pain reliever posed health risks for their children.

The manufacturers say autism and ADHD are genetic disorders and there is no conclusive evidence to support claims that in-utero exposure to acetaminophen raises risks. They are asking the presiding judge to bar plaintiffs from introducing testimony and studies that suggest the pain reliever might alter fetal development.

The catalyst for the lawsuits was a 2021 statement in the medical journal Nature Reviews Endocrinology, supported by more than 90 scientists and health professionals, that called for increased awareness and research into the potential risks of prenatal exposure to the drug.

The plaintiffs’ lawyers, representing families who have children with ADHD or autism, are seeking to cite scientific research to establish that environmental factors, including taking acetaminophen, can influence fetal development.

“There is a reason so many prominent scientists have issued a call to action," said Ashley Keller, one of the lead plaintiffs’ lawyers for the consolidated litigation. “Pregnant women are entitled to that vital information so they can make well-informed healthcare decisions for themselves and their unborn children."

Tylenol is currently manufactured by Kenvue, a consumer-health company spun off from Johnson & Johnson. Many leading retailers and drugstore chains sell their own generic versions. Defendants in the cases include CVS Health, Walmart and Walgreens.

“There is the potential for unfortunate, real, and long-term public health consequences in allowing scientific guesswork in courtrooms to inform medical decision-making," a Kenvue spokeswoman said. The drug retailers declined to comment.

U.S. District Judge Denise Cote in Manhattan is scheduled to consider the issue at a Thursday hearing. If she decides the plaintiffs’ evidence is admissible, it could spark a flood of similar lawsuits. If the companies prevail, the litigation could quickly fall apart.

“The science is a big issue and will make or break the case," said Elizabeth Burch, a law professor at the University of Georgia.

Acetaminophen has long been deemed the safest option for pain relief during pregnancy, a fact noted by the American College of Obstetricians and Gynecologists. The group said there is no clear evidence that proves a direct relationship between the drug and any fetal-development issues.

In April, Cote asked the federal government whether any recent evidence warrants adding a warning about the use of acetaminophen during pregnancy. The Food and Drug Administration, represented by the Justice Department, declined in a September letter to weigh in on the litigation, but said scientific findings on the issue are inconsistent and limited.

Acetaminophen labels currently advise pregnant women to speak to their doctor before taking the drug, but plaintiffs say this is insufficient. Roughly 65% of expecting mothers use the drug, and doctors frequently advise using it over other painkillers during pregnancy, they say.

Given the widespread use of the drug, as well as the prevalence of diagnoses of autism and ADHD, the litigation could grow exponentially if the judge gives plaintiffs wide latitude to establish a correlation.

“People are waiting to see if we survive," said Roger Smith, a lawyer representing plaintiffs in the litigation. “Once we do, hundreds and even thousands of cases will be filed relatively quickly."

Since May 2022, there have been 34,000 television advertisements soliciting claims, at an estimated cost of $5.4 million, according to X Ante, which tracks marketing and advertising spending for mass torts. In a recent report, the group found that spending on acetaminophen-claim advertising jumped nearly sevenfold from August to September.

The pharmaceutical industry has been pummeled with mass-tort litigation for years, including cases resulting in large settlements by opioid manufacturers and pharmacies which faced allegations that they didn’t do enough to stop the epidemic.

This stage of litigation can derail a case. For example, in a case consolidated in a federal Florida court, involving roughly 2,400 lawsuits claiming heartburn medication Zantac caused cancer, a judge said the science wasn’t strong enough to move the cases forward. A separate state-consolidated case was later settled.

The acetaminophen case has the potential to be huge but the legal standards for admitting scientific studies and expert testimony are rigorous and can make life difficult for plaintiffs, said Adam Zimmerman, a law professor at the University of Southern California.

“It’s an incredibly high hurdle to meet in these cases," Zimmerman said.

Write to Erin Mulvaney at erin.mulvaney@wsj.com