FDA researchers have uncovered new evidence of a molecular link between one of the best-selling drugs in U.S. history—an asthma medication initially developed by Merck and marketed under the brand name Singulair (montelukast)—and severe mental health issues in some patients. Nonetheless, according to Reuters, the FDA does not intend to update the label of montelukast products to reflect these latest findings. FDA researchers wrote in their abstract:
“Emerging data from confirmatory pharmacology studies in primary human CNS cells treated with montelukast and endogenous receptor ligands provide further insight into potential molecular mechanisms of drug-related [central nervous system] effects. This report is the first public release [of these findings].”
The research indicates that montelukast attaches to several brain receptors critical to psychiatric functioning. Singulair, launched in 1998, was a blockbuster money-maker product for Merck, offering a convenient pill-based alternative to inhalers. It comes as no surprise to learn that early marketing campaigns claimed the drug’s side effects were as negligible as those of a “sugar pill,” and its label described minimal brain distribution. Millions of adults and children still use generic versions annually.
However, by 2019, thousands of reports of neuropsychiatric issues, including numerous suicides, had surfaced in the FDA’s adverse event database and online forums, according to Reuters. While they insist such reports do not prove a causal relationship, like the millions of adverse events following the deadly mRNA COVID jabs, they should prompt swift further investigation. Following analysis in 2020, the FDA added a “black box” warning to Montelukast, highlighting severe mental health risks, including suicidal thoughts and actions. In announcing the warning, an FDA Drug Safety Communication stated:
“We continue to receive reports of mental health side effects reported with montelukast use. Consistent with our prior evaluations, a wide variety of mental health side effects have been reported, including completed suicides. Some occurred during montelukast treatment and resolved after stopping the medicine. Other reports indicated that mental health side effects developed or continued after stopping montelukast.”
Around the same time that the “black box” warning was issued, the FDA assembled an expert panel to explore the drug’s potential to trigger neuropsychiatric side effects. Preliminary findings from this group, not previously reported or publicly released, were presented at the American College of Toxicology meeting in Austin, Texas, in November 2024. Jessica Oliphant, deputy director at the FDA’s National Center for Toxicological Research, reported that laboratory tests revealed “significant binding” of montelukast to multiple brain receptors. Additional studies established that montelukast penetrates rat brains, suggesting accumulation in regions involved in psychiatric effects. Calling for further research on the drug’s impact on the nervous system, Oliphant remarked:
“These data indicate that montelukast is highest in brain regions known to be involved in (psychiatric effects).”
Again, despite these disturbing findings, the FDA stated it has no immediate plans to update the drug’s label based on the presentation. The drug’s behavior parallels that of medications known to cause neuropsychiatric effects, like the antipsychotic risperidone, according to FDA slides reviewed by Reuters. A Merck representative did not respond to questions. Organon, a Merck spinoff that now markets Singulair, issued a statement declaring it is confident in the drug’s safety profile, stating that the label appropriately details its risks and benefits.
The 2020 “black box” warning resulted from research from Julia Marschallinger and Ludwig Aigner of Austria’s Institute of Molecular Regenerative Medicine. They told Reuters the new findings underscore the presence of montelukast in the brain, noting that affected receptors are integral to mood, impulse control, cognition, and sleep. While the exact mechanism and patient risk factors remain unclear, Marschallinger emphasized that the data supports patient reports of side effects. “It’s definitely doing something that’s concerning,” she said.
Reuters previously reported in 2023 that the FDA had received thousands of reports of patients, including many children, experiencing depression, suicidal thoughts and behaviors, or other psychiatric problems after they began using montelukast. Before that, by 2019, the FDA calculated 82 suicides linked to Singulair and its generic versions reported to its adverse-event database since 1998. Over ten years. Concerningly, at least 31 of those accounts involved individuals aged 19 or younger.
One such case was 22-year-old Nick England of Virginia, who died by suicide in 2017, less than two weeks after starting montelukast. His father, Robert England, recalls that Nick was healthy with no prior mental health concerns but experienced difficulty sleeping shortly before his death. “He was on that medication for just days, literally just days,” England said. “It completely changed the trajectory of our lives.”
Lawsuits have alleged that Merck was aware of montelukast’s potential to affect the brain early in its development but downplayed these risks in communications with regulators. Many of these cases remain unresolved. Like the others—insistent that their son had no history of mental health problems—following his death, England’s parents began exploring a lawsuit against Merck, along with the manufacturer of the generic version their son took. They were shocked to learn that they had no case. Emphasizing how Merck and others remain unaccountable, Reuters wrote:
“Like countless other potential plaintiffs, they had run into one of Corporate America’s most effective liability shields: the legal doctrine of preemption, the principle that federal law supersedes state law.
Armed with U.S. Supreme Court rulings on preemption starting in the 1990s, companies increasingly argue that federally regulated products or services should be immune from lawsuits alleging state-law violations. In a new reading of an old constitutional principle, judges have held that federal law, including the decisions of U.S. regulatory agencies, should preempt, or override, state statutes that seek to hold companies accountable for harming consumers.
State laws historically have provided the legal basis for some of the most common lawsuits against U.S. companies alleging injuries, deaths, or illnesses caused by negligence or defective products.”
