A federal judge denied the dismissal of federal lawsuits that allege that the children of women who took Tylenol while pregnant developed autism or attention deficit hyperactivity disorder (ADHD) because of the drug’s active ingredient, acetaminophen. In response, Johnson & Johnson (J&J) filed a motion for a rare type of appeal called an interlocutory appeal, which would allow J&J to seek a federal appeals court decision on whether the failure to provide adequate warnings should be preempted by federal law.

Plaintiffs in the acetaminophen lawsuits, which also name several large drug store chains as defendants, claim that they believed that using Tylenol during pregnancy posed minimal risks to developing children because there was no warning label about the risk of autism or ADHD. However, some studies have shown a correlation. 

For instance, a 2010 study in a quarterly, peer-reviewed journal, Acta Neurobiologiae Experimentalis, noted that “Acetaminophen use in children has been associated with increased autism risk. Recent evidence suggests that acetaminophen's analgesic actions result from activation of the endocannabinoid system, and activation of this system can have neuromodulatory consequences during development.” The study was conducted to determine if there was sufficient evidence to support this hypothesis.

More recently, a 2021 meta-analysis in the European Journal of Epidemiology, which looked at six distinct European populations covering 73,881 mother-child pairs, concluded “children prenatally exposed to acetaminophen were 19% and 21% more likely to subsequently have borderline or clinical Autism Spectrum Conditions (ASC) and ADHD symptoms compared to non-exposed children. However, the study had no control group and did not factor in external causes since it was a strictly observational study.

As of May 1, over 100 families are pursuing Tylenol lawsuits against J&J over claims that the company violated state laws by failing to warn pregnant women about the potential risks associated with acetaminophen. Considering the popularity of acetaminophen, which is included in several other over-the-counter medicines, and the steadily increasing rates of autism and ADHD diagnosis—statistics from the CDC reveal that 1 in 36 children have been estimated to be identified with autism spectrum disorder (ASD)—legal experts believe that the number of Tylenol lawsuits will grow exponentially. 

The Tylenol lawsuits filed in federal courts have been consolidated in multidistrict litigation (MDL) in the Southern District of New York. 

J&J had sought to dismiss the Tylenol autism/ADHD lawsuits in February, claiming that FDA regulations did not require the company to put a warning label on its acetaminophen products, and since federal labeling laws trump state labeling laws, the company could not place a stronger pregnancy warning.  

However, on April 20, the U.S. District judge overseeing the Tylenol lawsuits, Judge Denise Cote, rejected this argument, ruling that J&J could have added warnings about the risks of exposure to acetaminophen without violating federal law.

J&J’s request for an interlocutory review of the preemption order would be independent of a final judgment on whether Tylenol contributed to any individual child's diagnosis of ADHD or autism. If J&J’s request is denied or is reviewed but the preemption argument is rejected, Judge Cote may schedule the first test cases called bellwether trials in the MDL.