Propranolol is a non-selective beta-blocker. Which statement describes its cardiovascular effect?

Propranolol is a non-selective beta-blocker. Which statement describes its cardiovascular effect?

• A. Decreases cardiac output
• B. Increases renin secretion
• C. Increases heart rate
• D. Causes vasoconstriction

Answer: (A)

Blockade of beta-1 receptors in the heart reduces both heart rate and the force of contraction, which lowers how much blood the heart pumps with each beat and overall cardiac output. Propranolol, being non-selective, also blocks beta-2 receptors, but the dominant cardiovascular effect you’ll see clinically is a fall in cardiac output due to negative chronotropy and inotropy. It also reduces renin release from the juxtaglomerular cells, which can contribute to lower blood pressure over time. Because heart rate is decreased and contractility is reduced, saying that cardiac output falls best captures the main cardiovascular impact of this drug. The ideas that it increases heart rate or causes vasoconstriction are not the primary effects in this context.

Blockade of beta-1 receptors in the heart reduces both heart rate and the force of contraction, which lowers how much blood the heart pumps with each beat and overall cardiac output. Propranolol, being non-selective, also blocks beta-2 receptors, but the dominant cardiovascular effect you’ll see clinically is a fall in cardiac output due to negative chronotropy and inotropy. It also reduces renin release from the juxtaglomerular cells, which can contribute to lower blood pressure over time. Because heart rate is decreased and contractility is reduced, saying that cardiac output falls best captures the main cardiovascular impact of this drug. The ideas that it increases heart rate or causes vasoconstriction are not the primary effects in this context.