NCLEX Pharmacology Renal and Urinary Practice Exam

Hydrochlorothiazide is a thiazide diuretic that primarily lowers blood pressure by reducing blood volume through diuresis and decreasing peripheral vascular resistance. The mechanism involves two key actions:

1. **Diuresis**: Hydrochlorothiazide promotes the excretion of sodium and water from the kidneys. This process decreases blood volume, which directly contributes to lowering blood pressure. When there is less blood volume circulating in the system, the pressure exerted on arterial walls also decreases, resulting in a lower blood pressure.

2. **Decreased Peripheral Vascular Resistance**: In addition to reducing blood volume, thiazide diuretics like hydrochlorothiazide also have a mild vasodilatory effect on the smooth muscle of the blood vessels. This effect helps to reduce the resistance that blood encounters as it flows through the vessels, further facilitating a drop in blood pressure.

This dual mechanism of action—reducing blood volume and minimizing vascular resistance—is why Option B accurately describes how hydrochlorothiazide functions to reduce blood pressure. Other options focus on mechanisms such as increasing heart rate, directly dilating blood vessels, or blocking calcium channels, which are not the primary or relevant actions of hydrochlorothiazide in the management of hypertension.