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Pharmacology · single question

DAY 2 — CASE 4: A patient is taking atenolol. What is the mechanism of action?

  1. Decreases cardiac output
  2. Increases cardiac output
  3. Increases vascular resistance
  4. Decreases cardiac resistance (afterload)
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Correct answer: A. Decreases cardiac output

  • A. Atenolol is a SELECTIVE BETA-1 ADRENERGIC ANTAGONIST (cardioselective beta-blocker). By blocking β1 receptors in the heart, it decreases heart rate (negative chronotropy) and myocardial contractility (negative inotropy) → DECREASES CARDIAC OUTPUT. Used for hypertension, angina, and arrhythmias.
  • B. Atenolol DECREASES cardiac output — it blocks beta-1 receptors, reducing heart rate and contractility.
  • C. Atenolol does not increase vascular resistance. Alpha blockers reduce resistance; beta-blockers like atenolol are primarily cardiac.
  • D. Atenolol does not directly decrease cardiac resistance (afterload) — this is a property of vasodilators (e.g., ACE inhibitors, ARBs).

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