Nitroglycerin primarily causes what physiological effect?

• A. Vasoconstriction of peripheral arteries
• B. Vasodilation of coronary arteries
• C. Increased platelet aggregation
• D. Decreased heart rate

Answer: (B)

Nitroglycerin works by releasing nitric oxide, which relaxes vascular smooth muscle and causes vasodilation. This dilation lowers the heart’s oxygen demand by reducing preload (venodilation) and, to a lesser extent, afterload, and it also can widen coronary arteries to improve blood flow to ischemic areas. In this context, the effect that best matches its clinical use is the dilation of the coronary arteries, which helps relieve ischemia. The other statements don’t fit: it does not cause peripheral vasoconstriction, it does not increase platelet aggregation, and it does not typically decrease heart rate (more often it can cause reflex tachycardia).