Paper I
2021 February (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Prazosin

Q43 marksShort Notes

Answer

Prazosin is a selective α1-adrenergic receptor antagonist.

Mechanism of action

  • Selectively blocks postsynaptic α1 receptors in vascular smooth muscle, causing arteriolar and venous vasodilatation, reducing peripheral vascular resistance and blood pressure
  • Also blocks α1 receptors in prostatic/urethral smooth muscle, relaxing it and improving urine flow

Uses

  • Hypertension
  • Benign prostatic hypertrophy (symptomatic relief)

Adverse effects

  • First-dose hypotension/syncope
  • Postural hypotension
  • Dizziness, headache
  • Reflex tachycardia (less than with pure vasodilators)
  • Fluid retention with chronic use

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