Mechanism of action of thiazides is by –
**Core Concept**
Thiazides are a class of diuretics used in the management of hypertension and edema. They exert their effect by inhibiting the reabsorption of sodium and chloride ions in the distal convoluted tubule (DCT) of the nephron.
**Why the Correct Answer is Right**
Thiazides act by inhibiting the sodium-chloride cotransporter (NCC) in the DCT. This leads to an increase in the excretion of sodium and chloride ions, resulting in a decrease in blood volume and subsequently, a decrease in blood pressure. The NCC is a key player in the regulation of electrolyte balance in the body, and its inhibition by thiazides leads to a decrease in the reabsorption of sodium and chloride ions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option does not accurately describe the mechanism of action of thiazides. Thiazides do not act by inhibiting the angiotensin-converting enzyme (ACE) like ACE inhibitors.
**Option B:** This option is incorrect as thiazides do not act by blocking the calcium channels in the smooth muscle like calcium channel blockers.
**Option C:** This option is incorrect as thiazides do not act by inhibiting the aldosterone receptors like mineralocorticoid receptor antagonists.
**Clinical Pearl / High-Yield Fact**
Thiazides have a long half-life and can be used once daily, making them a convenient option for patients with hypertension. However, they can cause hypokalemia and hyperglycemia as side effects.
**Correct Answer: D. Inhibition of the sodium-chloride cotransporter (NCC) in the distal convoluted tubule (DCT).**