• The Review Course in Family Medicine

Update on Antihistamines - When should they never be prescribed?



Rule #1


Antihistamines should only be used to treat allergic rhinitis, urticaria, and conjunctivitis.

Do NOT use for asthma, eczema, cough, or insomnia management.


Rule #2


Be mindful of the side-effect profile associated with first-generation antihistamines, including the anticholinergic and anti-alpha-adrenergic properties which can result in prolonged QT and death.

DO NOT use in elderly populations or with alcohol.


Rule #3


Stick to the approved list: Bilastine, Cetirizine, Desloratadine, Fexofenadine, Loratadine and Rupatadine. These newer antihistamines should be selected when available. Their heightened safety profile and increased duration and speed of action make them a much preferable choice.


Rule #4


DO NOT replace epinephrine with antihistamines in the treatment of anaphylaxis.

Antihistamines MAY be used in ADDITION but beware of hypotension.


Rule #5


Do not be afraid to use antihistamines in pregnant or breastfeeding women or children; they have been deemed safe in both these populations.

Inadequate evidence regarding rupatadine and bilastine




How to use antihistamines

CMAJ April 06, 2021 193 (14) E478-E479; DOI: https://doi.org/10.1503/cmaj.201959

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