Merck Sued Over Asthma Drug’s Alleged Psychiatric Effects

Merck & Co. Inc. has been hit with a lawsuit in New Jersey state court by a woman who claims her use of asthma medicine Singulair as a teen led to neuropsychiatric disorders and the pharmaceutical giant belatedly warned consumers despite its longtime knowledge of the drug’s risks.

Rachel McHenry and her mother, Brenda Lee Danielson, trace the history of Singulair from Merck’s patent application in 1996 to the company’s insertion of a serious label warning about a year ago. They say extensive, ongoing testing of the drug’s active ingredient montelukast indicates a link between its use and the maladies that plague McHenry.

Singulair is used for the prophylactic and chronic treatment of asthma and the prevention of exercise-induced bronchoconstriction and to treat symptoms of allergic rhinitis, according to the complaint.

It wasn’t until March 2020 that Merck, on orders from the U.S. Food and Drug Administration, added a “black box” warning — the most serious type — regarding neuropsychiatric events, along with a new medication guide, according to the complaint.

The black box label warning lists about three dozen possible side effects, including anxiousness, depression, hallucinations, sleepwalking and tremors, according to the complaint.

The complaint lodges claims of design defect, failure to warn, negligence, and breach of express and implied warranties. McHenry and Danielson are seeking compensatory, consequential and punitive damages, along with attorney fees and court costs.

The plaintiffs say they know of nine other lawsuits that have been filed in state court over Singulair side effects and plan to request a multicounty litigation designation.


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