First-line treatment for anaphylaxis is which intervention?

• A. Diphenhydramine
• B. Intramuscular epinephrine
• C. Albuterol inhalation
• D. Atropine

Answer: (B)

Anaphylaxis needs a rapid, multi-faceted reversal of airway swelling, bronchospasm, and shock. Epinephrine given by injection into the muscle provides that broad, life-saving effect because it combines alpha-1–mediated vasoconstriction (reducing edema and raising blood pressure), beta-1–mediated increases in heart rate and contractility (improving perfusion), and beta-2–mediated bronchodilation plus stabilization of mast cells to limit further mediator release. This makes it the fastest and most effective initial treatment, and it should be given immediately.

Adjuncts like diphenhydramine can help with itching or hives but do not reverse airway obstruction or hypotension and should not delay epinephrine. Albuterol can help with bronchospasm if needed after epinephrine, but it does not treat the shock. Atropine has no role in treating anaphylaxis. In adults, the typical dose is 0.3–0.5 mg of 1:1000 epinephrine IM, repeated as needed; for children, 0.01 mg/kg per dose, up to 0.3 mg per dose, with repeats as necessary.