**Core Concept**
Lithium-induced polyuria is a clinical condition where patients with lithium treatment experience increased urine production, leading to dehydration and electrolyte imbalances. This occurs due to the inhibition of the renin-angiotensin-aldosterone system (RAAS) and the subsequent decrease in antidiuretic hormone (ADH) secretion.

**Why the Correct Answer is Right**
The drug of choice in lithium-induced polyuria is a non-steroidal, non-peptide vasopressin receptor 2 (V2) agonist, which helps to increase water reabsorption in the collecting ducts of the kidneys. This mechanism is particularly effective in counteracting the effects of lithium on ADH secretion and the RAAS. **Desmopressin** is a synthetic analogue of ADH that specifically activates the V2 receptors, thereby increasing water reabsorption.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not address the pathophysiology of lithium-induced polyuria.
* **Option B:** This option is incorrect as it does not specifically target the V2 receptors in the collecting ducts of the kidneys.
* **Option D:** This option is incorrect as it may not be effective in counteracting the effects of lithium on ADH secretion and the RAAS.

**Clinical Pearl / High-Yield Fact**
Lithium-induced polyuria is a common side effect of lithium treatment, and **desmopressin** is a highly effective treatment option. It is essential to monitor lithium levels and adjust the dosage accordingly to prevent this condition.

**Correct Answer:** A. Desmopressin.