A patient develops an acute severe allergic-like reaction to iodinated contrast medium 15 minutes after IV administration, with urticaria, bronchospasm, hypotension, and loss of consciousness. This reaction is classified as anaphylactoid (non-IgE mediated). What is the FIRST-LINE drug treatment?
- A Intramuscular adrenaline (epinephrine) 0.5 mg (1:1000 solution) to the anterolateral thigh ✓
- B IV chlorphenamine (antihistamine) 10 mg
- C IV hydrocortisone 200 mg
- D IV salbutamol for bronchospasm
Correct answer: A. Intramuscular adrenaline (epinephrine) 0.5 mg (1:1000 solution) to the anterolateral thigh
Explanation
In anaphylaxis (whether IgE-mediated or anaphylactoid), the FIRST-LINE and most critical treatment is intramuscular adrenaline (epinephrine) 0.5 mg (0.5 mL of 1:1000) into the anterolateral thigh — NOT IV (risk of fatal arrhythmia if given IV in wrong concentration). Adrenaline reverses bronchospasm, vasodilation, and angioedema. Antihistamines and corticosteroids are adjunctive (delayed action) and do not reverse life-threatening anaphylaxis. This applies to contrast reactions as per ACR and ESUR guidelines.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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