Which of the following drugs is an alpha-blocker?

Appeared in: DSSSB 14 August 2024

Explanation

Prazosin is classified as a selective alpha-1 adrenergic receptor antagonist, commonly known as an alpha-blocker.
Its primary mechanism of action is to block alpha-1 receptors on vascular smooth muscle, which causes both arterioles and veins to dilate.
This vasodilation leads to a reduction in total peripheral resistance, resulting in a decrease in blood pressure.

Option A: Propranolol is a non-selective beta-blocker. It acts by blocking both beta-1 and beta-2 adrenergic receptors, primarily affecting the heart to reduce heart rate and contractility.
Option B: Nifedipine is a dihydropyridine calcium channel blocker. It works by inhibiting the influx of calcium ions into vascular smooth muscle cells, causing vasodilation.
Option C: Verapamil is a non-dihydropyridine calcium channel blocker. It affects both cardiac muscle (reducing heart rate and contractility) and vascular smooth muscle (causing vasodilation).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology: Classification of Antihypertensive Drugs as background academic context rather than a clinical decision trigger.
A critical nursing consideration for Prazosin is the 'first-dose effect,' which can cause significant postural hypotension and syncope. Nurses must instruct patients to take the first dose at bedtime to minimize this risk and to rise slowly from sitting or lying positions.
What if? If a patient with hypertension also has benign prostatic hyperplasia (BPH), an alpha-blocker like Prazosin is an excellent therapeutic choice as it addresses both conditions simultaneously. It lowers blood pressure and improves urinary flow by relaxing smooth muscle in the prostate and bladder neck.

How to Approach the Question

This is a factual recall question from pharmacology.
First, identify the core requirement of the question: to find the 'alpha-blocker'.
Next, systematically review each option and recall its specific drug class.
Propranolol is a well-known beta-blocker.
Nifedipine and Verapamil are common calcium channel blockers.
Prazosin is a classic example of an alpha-blocker. This matches the question's requirement, making it the correct answer.

Concept Tested & Keywords

QXTp-lSFrswqFaJuyDAN19

E6 Pharmacology Katzung 16e p. 245-247

E6 Pharmacology Nurses Shanbhag 3e p. 89-91

E6 Pharmacology KD Tripathi Essentials 9e Part 1 p. 183-185

Practise the full DSSSB 14 August 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.