In terms of antihypertensive therapy, diuretics predominantly decrease:

• A. Cardiac output
• B. Blood volume
• C. Vascular resistance
• D. Heart rate

Answer: (B)

Diuretics primarily function by promoting the excretion of sodium and water through the kidneys, which decreases the overall blood volume in the circulatory system. When blood volume is reduced, there is less fluid circulating within the blood vessels, leading to a decrease in the pressure exerted on vessel walls, which effectively lowers blood pressure. This reduction in blood volume is the fundamental mechanism through which diuretics exert their antihypertensive effect.

While the reduction in blood volume can indirectly influence other factors such as cardiac output and vascular resistance, the direct and most significant action of diuretics in hypertension management is on blood volume. Thus, understanding this mechanism is essential for grasping how diuretics achieve their therapeutic effects in the treatment of hypertension.