All Sample Questions

Mechanism of Action of Metoprolol 1

Question

Vignette: A 60-year-old man with a history of hypertension and diabetes presents to the clinic for a routine check-up. His blood pressure is 160/90 mmHg, and his glucose is 180 mg/dL. He is currently taking metoprolol and glipizide. Which of the following best explains the mechanism of action of one of his medications?

Choices

A) Inhibition of alpha-glucosidase in the intestinal brush border

B) Inhibition of ATP-sensitive potassium channels in the pancreatic beta cells

C) Blockade of beta-1 adrenergic receptors

D) Inhibition of angiotensin-converting enzyme

E) Blockade of voltage-gated sodium channels in the myocardium

Answer

C) Blockade of beta-1 adrenergic receptors

Explanation

The patient in the vignette is taking metoprolol, a beta-blocker, for his hypertension. Beta-blockers function by blocking beta-1 adrenergic receptors, mainly located in the heart and kidneys. In the heart, this blockade leads to decreased heart rate, decreased contractility, and decreased conduction velocity, all of which contribute to a decrease in blood pressure. In the kidneys, beta-blocker use leads to a decrease in renin secretion, which also helps to lower blood pressure. Thus, the mechanism of action of metoprolol is best described as the blockade of beta-1 adrenergic receptors. The rest of the options represent mechanisms of action of other antihypertensive and antidiabetic drugs, but they do not apply to metoprolol or glipizide.