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Pharmacology · single question

What is the mechanism of action of nitroglycerin?

  1. Inhibits COX enzymes
  2. Activates guanylyl cyclase via release of nitric oxide
  3. Increases cAMP
  4. Blocks calcium channels
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Correct answer: A. Inhibits COX enzymes

  • A. Correct. Nitroglycerin releases nitric oxide (NO) in smooth muscle, which activates guanylyl cyclase → increases cGMP → smooth muscle relaxation → vasodilation. This reduces cardiac preload and afterload, relieving angina.
  • B. Incorrect. cAMP is increased by beta-agonists and phosphodiesterase inhibitors. Nitroglycerin works through cGMP.
  • C. Incorrect. COX inhibition is the mechanism of NSAIDs like aspirin and ibuprofen.
  • D. Incorrect. Calcium channel blockers (amlodipine, verapamil) are a separate drug class.

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