Other safety alerts
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| Canada: Summary Safety Review: Oral, over-the-counter diphenhydramine-containing products: Assessing the potential risk of serious side effects in children |
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Health Canada announces that it assessed the potential risk of serious side effects in children of oral, over-the-counter (OTC) diphenhydramine-containing products (DCPs).
Most DCPs are authorized for sale in Canada as OTC drugs to relieve symptoms of several medical conditions, including allergies. They belong to a group of drug products known as first-generation antihistamines.
In 2019, the Canadian Society of Allergy and Clinical Immunology (CSACI) published a position statement recommending the use of newer-generation antihistamines for the treatment of hay fever (allergic rhinitis) and hives (urticaria) because of the side effects associated with first-generation antihistamines. The statement did not identify new safety information for first-generation antihistamines, however, it generated interest from the Canadian public about the safety of DCPs at recommended or higher doses, specifically in children.
Diphenhydramine has the potential for problematic use and overdose that can lead to serious side effects in children, including seeing and hearings things that are not there (hallucinations), sudden change in the brain's normal electrical activity (seizures), palpitations, difficulty in breathing and coma. The use of DCPs to treat allergic symptoms is widespread, particularly in children. As a precaution, Health Canada assessed known and potential serious side effects associated with the use of DCPs in children under 2 years of age, and serious side effects related to problematic use and accidental overdose in children under 18 years of age. The purpose of the review was to determine if there was a change in the type and/or frequency of side effects associated with the use of DCPs in these vulnerable populations.
Health Canada reviewed the available information from searches of the Canada Vigilance database, published literature, and the manufacturer. Health Canada reviewed 52 Canadian case reports involving diphenhydramine use in children, received between Dec 1983 and Mar 2019; none were fatal. Of the 52 cases, only 5 contained enough information to determine whether there was a link between the use of diphenhydramine and the reported serious side effects in children:
- One case involved a child under 2 years of age with difficulty in controlling movements (dyskinesia); this case was found to be probably linked with the use of oral diphenhydramine at the recommended dose.
- Four cases involved problematic use or overdose in children. Reported side effects included false beliefs (delusions), hallucinations, disorientation, dizziness, hyperactivity, widened (dilated) pupils, rapid heart rate (tachycardia), and seizure, alone or accompanied by vomiting. Two cases were found to be probably linked, and 2 were found to be possibly linked with the use of oral diphenhydramine.
Health Canada also reviewed international literature cases. The side effects reported in these cases were consistent with the known safety profile of diphenhydramine.
Health Canada's review of the available information found no change in the type or frequency of serious side effects associated with the use of DCPs to warrant regulatory action at this time.
Please refer to the following website in Health Canada for details:
http://hpr-rps.hres.ca/../summary-safety-review-detail.php?lang=en&linkID=SSR00282
In Hong Kong, there are 61 registered pharmaceutical products containing diphenhydramine which are in oral dosage forms. All products are pharmacy only medicines. So far, the Department of Health (DH) has received one case of adverse drug reaction related to diphenhydramine, but this case was not related to drug use in children. The DH will remain vigilant on safety update of the drug issued by other overseas drug regulatory authorities.
Ends/Wednesday, Mar 2, 2022
Issued at HKT 14:00
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