Paper I
2017 February (2010 Scheme) · 40 marks · 120 min

Question

Classify drugs used in the treatment of angina pectoris. What is the effect of nitrates on coronary blood flow. Describe the mechanism of action and any two adverse effects of nitrates. (2+1+2+1 =6)

Q16 marksEssays

Answer

Classification of antianginal drugs

  • Nitrates: Glyceryl trinitrate, Isosorbide dinitrate
  • Beta blockers: Atenolol, Propranolol
  • Calcium channel blockers: Amlodipine, Verapamil, Diltiazem
  • Potassium channel openers: Nicorandil
  • Others: Ranolazine, Ivabradine

Effect of nitrates on coronary blood flow

  • Nitrates dilate epicardial coronary arteries and collateral vessels, redistributing blood flow toward ischaemic subendocardial areas, and relieve coronary vasospasm — thereby improving oxygen supply to ischaemic myocardium (in addition to their major effect of reducing oxygen demand via venodilatation)

Mechanism of action

  • Nitrates release nitric oxide (NO), which activates guanylyl cyclase, increasing cGMP and causing smooth muscle relaxation
  • Predominant venodilatation reduces preload (venous return), reducing left ventricular wall tension and myocardial oxygen demand; also some arteriolar dilatation (↓afterload)

Adverse effects

  • Headache (due to cerebral vasodilatation)
  • Postural hypotension, reflex tachycardia
  • Flushing
  • Tolerance with continuous use (requires a nitrate-free interval)

Other Years Asked


Revise MBBS
Preview