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- Page navigation anchor for RE: Missing the point in recommendationsRE: Missing the point in recommendations
This article is welcome, but the authors miss the point on several issues.
First: Antihistamines are commonly and incorrectly used, largely because they are bought off the shelf in pharmacies, and professionals – whether physicians or pharmacists – have little influence on how they are used. Most products on the shelves contain diphenhydramine: very sedating. They are marketed for the purposes that this article questions: insomnia, cough, and eczema. People keep buying them because they perceive them as effective, without good alternatives. We need to listen to the customers more. In particular, while antihistamines are ineffective against many infectious coughs, they treat the “clearing the throat” cough that often accompanies allergic rhinitis, and may be a pathognomonic sign.
Second: First generation antihistamines are associated with serious side effects, but there is no clear distinction between the first and later generation drugs, but a gradation. Among the three available in Canada, diphenhydramine and hydroxyzine are most sedating, while chlorpheniramine is less so. The quoted half-lives are based on cutaneous wheal and flare reactions, but many patients find the sedating effect of diphenhydramine 25mg lasts up to 12 hours, while sedative effects of chlorpheniramine 4mg are not perceptible on wakening in the morning. Among the second-generation antihistamines the WHO review1 shows that cetirizine is more sedating, but it is unclear whether there is...
Show MoreCompeting Interests: None declared.References
- Chahal H [for WHO Secretariat]. Section 3: Antiallergics and medicines used in anaphylaxis: histamine-1 receptor antagonists — a critical evaluation to update Section 3. Geneva: The World Health Organization; 2012.
- Consumer Reports Best Buy Drugs: Using antihistamines to treat allergies, Hay Fever and Hives. 2013 www.consumerreports.org
- Fein MN, Fischer DA, O’Keefe AW, et al. CSACI position statement: newer generation H1-antihistamines. Allergy Asthma Clin Immunol 2019;15:61.
- Page navigation anchor for RE: How to use antihistaminesRE: How to use antihistamines
The section entitled, "Antihistamines Should Not Be Used Instead Of Epinephrine To Treat Anaphylaxis". While I agree with this in principle the authors are not specific as to whether they mean the use of newer antihistamines orally. Secondly in patients who are in extremis, the administration of oral medications is ill advised if they can be avoided. Anaphylaxis can be life threatening. Treatment advice should be precise and unambiguous.
Competing Interests: None declared.References
- Derek K. Chu, Paul Oykhman, Gordon L. Sussman. How to use antihistamines. CMAJ 2021;193:E478-E479.