Which of the following is an alpha-1 blocker?

• A. Prazosin
• B. Metoprolol
• C. Lisinopril
• D. Hydrochlorothiazide

Answer: (A)

Alpha-1 blockers work by blocking alpha-1 adrenergic receptors on vascular smooth muscle, which prevents norepinephrine from constricting those vessels. That causes dilation of arteries and veins and lowers blood pressure, though a common first-dose drop in blood pressure can occur.

Prazosin is a classic alpha-1 blocker, used to treat hypertension and sometimes BPH-related symptoms because it directly prevents alpha-1–mediated vasoconstriction.

Metoprolol is a beta-1 selective blocker, reducing heart rate and contractility, not blocking alpha-1 receptors. Lisinopril is an ACE inhibitor that lowers angiotensin II levels, affecting blood pressure through a different pathway. Hydrochlorothiazide is a thiazide diuretic that decreases blood volume.