What injuries are alleged in the Singulair lawsuits?

Lawsuits allege depression, suicidal thoughts and behavior (including completed suicide), anxiety and agitation, aggression and irritability, sleep disturbances, nightmares, and insomnia, obsessive-compulsive symptoms, tics, tremors, and stuttering, other neuropsychiatric and mood/behavior changes. These are allegations; a court has not found that Singulair causes them.

Singulair Lawsuit

montelukast (montelukast sodium) · Merck & Co. (brand now held by Organon, a Merck spinoff); also widely sold as generic montelukast · updated June 2026

Singulair (montelukast) is an asthma and allergy drug that the FDA placed under a Boxed Warning on March 4, 2020 for serious mental-health (neuropsychiatric) side effects. Lawsuits allege the manufacturer failed to adequately warn that montelukast can cause neuropsychiatric injuries such as depression and suicidal thoughts and behavior. Plaintiffs' claims are unproven and no court has found that montelukast caused these injuries. As of mid-2026 the cases are coordinated in New Jersey state court (Multicounty Litigation No. 637, In Re: Singulair Litigation, Atlantic County); there is no federal MDL and no global settlement.

This page is general information about ongoing litigation and FDA safety actions — not medical or legal advice, and not a statement that Singulair caused any injury. Allegations described here are claims that have not been proven in court. Always consult a licensed professional.

What the lawsuits allege

Plaintiffs allege that the manufacturer of Singulair (montelukast) knew or should have known of a risk of serious neuropsychiatric injuries — including depression, mood and behavior changes, and suicidal thoughts and actions — yet failed to adequately warn patients and prescribers before the FDA required a Boxed Warning in March 2020. They further allege that the drug was marketed and prescribed for milder conditions such as allergic rhinitis where, plaintiffs contend, the risks outweighed the benefits, and that the company should have disclosed these dangers sooner. These are unproven allegations; no court has established that montelukast caused the claimed injuries.

Depression
Suicidal thoughts and behavior (including completed suicide)
Anxiety and agitation
Aggression and irritability
Sleep disturbances, nightmares, and insomnia
Obsessive-compulsive symptoms
Tics, tremors, and stuttering
Other neuropsychiatric and mood/behavior changes

FDA action

On March 4, 2020, the FDA required a Boxed Warning — its most prominent warning — for montelukast (Singulair) and all montelukast generics, strengthening an existing warning about serious mental-health (neuropsychiatric) side effects, including agitation, aggression, depression, sleep disturbances, and suicidal thoughts and behavior. The FDA also required a patient Medication Guide and advised restricting use for allergic rhinitis, stating montelukast should be reserved for patients with allergic rhinitis who do not respond adequately to, or cannot tolerate, other therapies and should not be a first-choice treatment for mild allergic rhinitis. This is a label/safety action, not a recall; the drug remains on the U.S. market.

Where the litigation stands

As of mid-2026 there is no federal multidistrict litigation (MDL): the U.S. Judicial Panel on Multidistrict Litigation has not consolidated Singulair cases. Instead, cases are coordinated in New Jersey state court as Multicounty Litigation No. 637 ("In Re: Singulair Litigation," master docket ATL-L-481-22), Superior Court of New Jersey, Law Division, Atlantic County. The litigation was centralized in Atlantic County by order of the New Jersey Supreme Court in early 2022 (the application cited roughly a few hundred cases around the time of consolidation; exact current case counts are not publicly reported). The court has established a bellwether trial discovery pool (an initial group of cases identified for discovery under its case-management orders), but as of mid-2026 no bellwether trial dates have been set and no global settlement has been reached; reports indicate a partial settlement covering some New Jersey cases was reached in 2025 while litigation otherwise continues. (Informational only; not legal advice.)

Frequently asked

What is the Singulair lawsuit about?: Plaintiffs allege that the manufacturer of Singulair (montelukast) knew or should have known of a risk of serious neuropsychiatric injuries — including depression, mood and behavior changes, and suicidal thoughts and actions — yet failed to adequately warn patients and prescribers before the FDA required a Boxed Warning in March 2020. They further allege that the drug was marketed and prescribed for milder conditions such as allergic rhinitis where, plaintiffs contend, the risks outweighed the benefits, and that the company should have disclosed these dangers sooner. These are unproven allegations; no court has established that montelukast caused the claimed injuries. As of mid-2026 there is no federal multidistrict litigation (MDL): the U.S. Judicial Panel on Multidistrict Litigation has not consolidated Singulair cases. Instead, cases are coordinated in New Jersey state court as Multicounty Litigation No. 637 ("In Re: Singulair Litigation," master docket ATL-L-481-22), Superior Court of New Jersey, Law Division, Atlantic County. The litigation was centralized in Atlantic County by order of the New Jersey Supreme Court in early 2022 (the application cited roughly a few hundred cases around the time of consolidation; exact current case counts are not publicly reported). The court has established a bellwether trial discovery pool (an initial group of cases identified for discovery under its case-management orders), but as of mid-2026 no bellwether trial dates have been set and no global settlement has been reached; reports indicate a partial settlement covering some New Jersey cases was reached in 2025 while litigation otherwise continues. (Informational only; not legal advice.)
What injuries are alleged in the Singulair lawsuits?: Lawsuits allege depression, suicidal thoughts and behavior (including completed suicide), anxiety and agitation, aggression and irritability, sleep disturbances, nightmares, and insomnia, obsessive-compulsive symptoms, tics, tremors, and stuttering, other neuropsychiatric and mood/behavior changes. These are allegations; a court has not found that Singulair causes them.
Has the FDA acted on Singulair?: On March 4, 2020, the FDA required a Boxed Warning — its most prominent warning — for montelukast (Singulair) and all montelukast generics, strengthening an existing warning about serious mental-health (neuropsychiatric) side effects, including agitation, aggression, depression, sleep disturbances, and suicidal thoughts and behavior. The FDA also required a patient Medication Guide and advised restricting use for allergic rhinitis, stating montelukast should be reserved for patients with allergic rhinitis who do not respond adequately to, or cannot tolerate, other therapies and should not be a first-choice treatment for mild allergic rhinitis. This is a label/safety action, not a recall; the drug remains on the U.S. market.

Sources