Which intravenous vasodilator is commonly used in hypertensive emergencies to rapidly reduce afterload?

• A. Nifedipine
• B. Lisinopril
• C. Nitroprusside
• D. Hydralazine

Answer: (C)

In a hypertensive emergency the goal is a rapid, controlled drop in blood pressure to limit ongoing end-organ injury, and the most suitable intravenous agent for this is nitroprusside. It acts directly on vascular smooth muscle to dilate both arterioles and veins, which lowers systemic vascular resistance and reduces left ventricular afterload almost immediately. Because its effects begin within seconds and are easily titratable, clinicians can promptly reach a target blood pressure and adjust as needed, often with continuous arterial-line monitoring to prevent overcorrection. Nitroprusside can shorten dependence on afterload, improving forward flow and myocardial oxygen balance, but it requires careful use: watch for hypotension, reflex tachycardia, and potential cyanide toxicity with prolonged use or renal impairment, so limit duration and monitor appropriately. The other options either have slower, less predictable onset or are not as readily controllable in the acute setting—for example, hydralazine tends to cause tachycardia and unpredictable responses, while nifedipine is less favored for acute IV control, and lisinopril is not the typical IV agent for rapid BP reduction.