What is the first-line drug for the management of anaphylaxis?

• A. Epinephrine (adrenaline) given intramuscularly
• B. Diphenhydramine IV
• C. Albuterol inhalation
• D. Hydrocortisone IV

Answer: (A)

Epinephrine given by intramuscular injection is the first-line treatment for anaphylaxis. It tackles the life-threatening features of the reaction by hitting multiple target receptors at once: alpha-1 causes constriction of swollen blood vessels, which reduces airway edema and supports blood pressure; beta-1 increases heart rate and contractility to improve cardiac output; beta-2 opens airways and helps stabilize mast cells, slowing further mediator release. This rapid, broad action can halt progression of airway obstruction, breathing difficulties, and shock.

The intramuscular route in the mid-outer thigh is preferred because it provides the fastest and most reliable absorption with the safest profile in an acute setting. Typical dosing for adults is about 0.3 to 0.5 mg, and it can be repeated every 5–15 minutes as needed until symptoms improve. In children, the dose is weight-based (roughly 0.01 mg/kg up to about 0.3 mg per dose).

Diphenhydramine, while helpful for itching and hives, does not reverse airway swelling or shock and should not replace epinephrine. Albuterol can help with bronchospasm but does not address the dangerous drop in blood pressure or airway edema. Hydrocortisone may prevent a late-phase reaction but acts slowly and is not useful as the initial life-saving measure.