All of the following drugs are useful in nephrogenic diabetes insipidus; except
**Core Concept**
Nephrogenic diabetes insipidus (NDI) is a condition characterized by the kidneys' inability to concentrate urine in response to antidiuretic hormone (ADH) due to impaired renal tubular function. This condition leads to excessive water loss and polyuria.
**Why the Correct Answer is Right**
In NDI, the primary issue is the kidneys' inability to respond to ADH. Therefore, drugs that increase ADH levels or its effect on the kidneys are useful in managing NDI. Desmopressin, a synthetic analogue of ADH, is commonly used to treat NDI. Other useful medications include indomethacin, which blocks prostaglandin synthesis and reduces polyuria, and chlorothiazide, a thiazide diuretic that can help increase water reabsorption in the kidneys.
**Why Each Wrong Option is Incorrect**
**Option A:** Vasopressin is not typically useful in NDI as it is a natural analogue of ADH and can stimulate the ADH receptors in the kidneys, exacerbating the condition.
**Option B:** Hydrochlorothiazide (not chlorothiazide) can actually worsen NDI by increasing sodium delivery to the collecting ducts, which can further impair water reabsorption.
**Option C:** Furosemide is a loop diuretic that increases urine production and is not useful in NDI; it may even worsen the condition.
**Clinical Pearl / High-Yield Fact**
Remember that the key to managing NDI is to increase water reabsorption in the kidneys, either by increasing ADH levels or by using medications that can bypass the ADH receptor mechanism.
**Correct Answer:** A. Vasopressin