What is the initial management of anaphylaxis in the emergency department?

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Anaphylaxis must be treated immediately with epinephrine because it rapidly reverses airway swelling, bronchoconstriction, and systemic vasodilation. The best initial management is giving epinephrine intramuscularly right away, using a dose of 0.3–0.5 mg from a 1:1000 solution, typically injected into the mid-outer thigh. This dose acts quickly to constrict blood vessels, reduce edema, and open the airways, buying time to secure the airway and support circulation.

Call for help and prepare airway and resuscitation equipment while you administer the injection. Place the patient supine if able, with legs elevated to improve venous return, and ensure a clear airway with high-flow oxygen available. Reassess promptly; if symptoms persist or recur, give a second IM dose after several minutes (commonly 5–15 minutes). Establish IV access and begin isotonic fluids to treat hypotension, and monitor closely for response and signs of biphasic reaction.

Adjuncts such as inhaled beta-agonists for bronchospasm, H1 and H2 antihistamines, and corticosteroids may be used as needed, but they do not replace epinephrine as the first-line treatment. The key is rapid epinephrine administration with ongoing monitoring and readiness to support the airway and circulation.