MONTREAL — A Quebec coroner is recommending that diphenhydramine — an antihistamine and sedative sometimes used to sleep better — should be better managed in pharmacies after the overdose death of an 18-year-old man south of Montreal in December 2023.
The young man, whose identity is not revealed in the report made public, died of acute diphenhydramine poisoning at his home in St-Mathias-sur-Richelieu.
On the morning of Dec. 11, 2023, the man was found by his mother in his bed, unconscious and laying on his back. Toxicological analysis found the man had a lethal level of diphenhydramine in his blood.
The drug is the sedating ingredient in some over-the-counter antihistamines including the brand Benadryl, among others.
The coroner found the circumstances surrounding the death raise questions about the uncontrolled availability of a potentially lethal over-the-counter substance. He noted there is consensus about the risks of poisoning among scientific bodies, but it's not stored behind the counter.
"I cannot understand why the sale of diphenhydramine … is not better controlled," coroner Vincent Denault wrote. "I can't understand why diphenhydramine is available over the counter, especially since Gravol, which also contains diphenhydramine, isn't available."
In a report dated from late April but released this week, the coroner wrote the man's death is attributed to the acute toxicity of diphenhydramine, a central nervous system depressant which if consumed in sufficient quantities causes fatal respiratory depression and irregular heartbeat, which can lead to fatal cardiac arrhythmias.
The coroner noted there were previously used empty jars and blister packs of diphenhydramine tablets in the man's bedroom.
"Was he taking them to sleep better? Could he have taken pills in the same way, but in larger quantities, during the night of December 10-11, 2023?" the coroner asked.
Denault noted it wasn't the first time deaths have occurred due to the drug. The coroner has already weighed in on three previous Quebec investigations.
There was an uptick around in 2020 after the so-called Benadryl TikTok challenge on social media invited users to consume large quantities of medication tablets containing diphenhydramine.
"The deaths of children have put a face to this dangerous trend," Denault wrote. "The scientific literature confirms that diphenhydramine is consumed in high doses for its euphoric and hallucinogenic effects, and that people have used it to commit suicide."
Denault's recommendation was for the provincial office of professions to take steps to amend regulations involving the sale of medicinal products, to classify diphenhydramine intended for oral administration in a section that requires more management by pharmacists.
That management would include creating a file, noting the sale and carrying out a pharmacological study of the file.
Denault also asked the coroner's office to share the report with the Collège des médecins du Québec — the province's College of Physicians — and the Ordre des pharmaciens du Québec, the body that oversees pharmacists in the province.
Jean-François Desgagné, president of the pharmacists' order, said this week the order would review the coroner's recommendation to reclassify the drug to assess the appropriateness of moving it behind the pharmacist's counter.
This report by The Canadian Press was first published May 10, 2025.
Sidhartha Banerjee, The Canadian Press
