Paper I
2013 September (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Discuss the rationale for the use of adrenaline in anaphylactic shock

Q91 marksShort Answers

Answer

Adrenaline is the drug of choice in anaphylactic shock because it acts rapidly at multiple receptor sites to reverse the life-threatening features of anaphylaxis:

  • α1 action: Vasoconstriction — reverses hypotension and reduces mucosal oedema/angioedema
  • β1 action: Increases heart rate and contractility — supports blood pressure and cardiac output
  • β2 action: Bronchodilatation — relieves bronchospasm/wheeze; also stabilizes mast cells, reducing further release of histamine and other mediators

Given IM (anterolateral thigh) as first-line, it is the only drug that addresses both the cardiovascular collapse and airway obstruction of anaphylaxis simultaneously; other drugs (antihistamines, corticosteroids) are adjunctive and slower in onset.

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