A 24-year-old woman develops generalized urticaria, stridor and hypotension minutes after an insect sting. Alongside airway support and fluids, what is the correct first-line drug regimen?
- A Hydrocortisone 200 mg intravenously
- B Chlorpheniramine 10 mg intramuscularly
- C Adrenaline 0.5 mg intramuscularly into the anterolateral thigh ✓
- D Adrenaline 1 mg intravenously as a bolus
Correct answer: C. Adrenaline 0.5 mg intramuscularly into the anterolateral thigh
Explanation
Intramuscular adrenaline 0.5 mg (0.5 mL of 1:1000) into the anterolateral thigh is the established first-line treatment in adult anaphylaxis, acting on alpha-1 to restore vascular tone, beta-1 to raise cardiac output and beta-2 to reverse bronchospasm. Intravenous bolus adrenaline is reserved for peri-arrest situations because of arrhythmia risk. Steroids and antihistamines are second-line adjuncts that act slowly and never substitute for adrenaline.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
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