Drug of choice for nephrogenic diabetes insipidus is:-
**Core Concept**
Nephrogenic diabetes insipidus (NDI) is a condition characterized by the kidneys' inability to concentrate urine in response to antidiuretic hormone (ADH). This results from impaired renal tubular function, often due to genetic mutations, lithium toxicity, or other nephrotoxic agents. The treatment aims to reduce urine output and manage hypernatremia.
**Why the Correct Answer is Right**
The drug of choice for NDI is **hydrochlorothiazide (HCTZ)**, a thiazide diuretic. Thiazides work by inhibiting sodium reabsorption in the distal convoluted tubule, which increases calcium and sodium excretion. This leads to a mild volume contraction, stimulating the renin-angiotensin-aldosterone system (RAAS), and subsequently increasing water reabsorption in the collecting ducts. This mechanism helps to reduce polyuria and hypernatremia in NDI patients.
**Why Each Wrong Option is Incorrect**
**Option A:** Desmopressin is incorrect because it is a synthetic ADH analogue, which is more effective in central diabetes insipidus (CDI) rather than NDI.
**Option B:** Indomethacin is incorrect because it is a nonsteroidal anti-inflammatory drug (NSAID) that can exacerbate NDI by inhibiting prostaglandin synthesis, which is essential for renal function.
**Option C:** Amiloride is incorrect because it is a potassium-sparing diuretic that can worsen hypernatremia and polyuria in NDI patients.
**Clinical Pearl / High-Yield Fact**
In patients with NDI, thiazide diuretics like HCTZ can be used to manage polyuria and hypernatremia. However, it's essential to monitor electrolytes and renal function closely, as thiazides can cause hypokalemia and hypomagnesemia.
**Correct Answer:** C. Hydrochlorothiazide.