Which drug reduces preload and afterload?

• A. Nitroglycerin (Nitrostat)
• B. Furosemide
• C. Morphine
• D. Dopamine

Answer: (A)

Nitroglycerin reduces both preload and afterload. It releases nitric oxide, causing venodilation that lowers venous return to the heart (preload), and also arterial dilation that lowers systemic vascular resistance (afterload). The net result is decreased left ventricular filling pressures and decreased afterload, which lowers myocardial oxygen demand and improves coronary perfusion.

Furosemide mainly lowers preload by diuresis, reducing circulating volume, but it doesn’t reliably reduce afterload. Morphine can cause venodilation and lessen preload, but it lacks a consistent effect on afterload. Dopamine’s effects vary with dose and can increase afterload via vasoconstriction at higher doses, so it’s not a preload/afterload reducer.