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Pharmacology · single question

What is the mechanism of action of nitroglycerin?

  1. Releases nitric oxide, which activates guanylyl cyclase to increase cGMP and cause vasodilation
  2. Inhibits adenylyl cyclase and increases cAMP
  3. Decreases intracellular calcium levels by blocking L-type channels
  4. Blocks beta-1 adrenergic receptors
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Correct answer: A. Releases nitric oxide, which activates guanylyl cyclase to increase cGMP and cause vasodilation

Nitroglycerin is a prodrug that is metabolized to nitric oxide (NO) in vascular smooth muscle. NO activates soluble guanylyl cyclase, which converts GTP to cyclic GMP (cGMP). Elevated cGMP activates protein kinase G, which ultimately reduces intracellular calcium concentration, leading to smooth muscle relaxation and vasodilation. Predominantly venodilating at low doses, nitroglycerin reduces preload and myocardial oxygen demand, relieving angina. In the dental office, sublingual nitroglycerin (0.3-0.4 mg) is the first-line emergency treatment for an acute angina attack.

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