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Epinephrine is the first line treatment for anaphylaxis, an acute potentially life-threatening allergic reaction. It is typically administered intramuscularly in the anterolateral thigh at a dose of 0.01 mg/kg of 1:1000 (1 mg/ml) solution to a maximum initial dose of 0.5 mg. Currently in Canada, epinephrine autoinjectors (EAI) are available in three doses, 0.15 mg, 0.30 mg, and 0.50 mg. There are currently no published studies comparing 0.3 mg and 0.5 mg EAIs in the paediatric or adult populations to compare clinical effectiveness. However, as weight increases above 30 kg, the percentage of the recommended 0.01 mg/kg epinephrine dose from an existing 0.3 mg EAI decreases resulting in potential underdosing. As such, The Canadian Society of Allergy and Immunology (CSACI) recommends that for those who weigh ≥ 45 kg, physicians could consider prescribing the 0.50 mg EAI based on shared decision making with patients.
Li, L. D. X., Abrams, E. M., Lavine, E., Hildebrand, K., & Mack, D. P. (2021). CSACI position statement: transition recommendations on existing epinephrine autoinjectors. Allergy, Asthma and Clinical Immunology, 17(1). https://doi.org/10.1186/s13223-021-00634-2