Drug of choice for neurogenic diabetes insipidus is:
**Core Concept**
Neurogenic diabetes insipidus is a condition characterized by the lack of antidiuretic hormone (ADH, also known as vasopressin) secretion by the posterior pituitary gland. This defect impairs water reabsorption in the kidneys, leading to excessive urine production and polydipsia.
**Why the Correct Answer is Right**
Desmopressin is a synthetic analogue of ADH that is specifically designed to bypass the liver's first-pass metabolism, allowing it to be effective when administered orally or intranasally. It has a longer duration of action and is more potent than natural ADH. Desmopressin acts on the V2 receptors in the collecting ducts of the kidneys, increasing water reabsorption and reducing urine production. This makes desmopressin an ideal treatment for neurogenic diabetes insipidus.
**Why Each Wrong Option is Incorrect**
* **Option A:** Vasopressin is the natural hormone, but it has a short duration of action and is not as potent as desmopressin. It requires intravenous administration and is often used in acute settings.
* **Option B:** Hydrochlorothiazide is a diuretic that would exacerbate the condition by increasing urine production, not treating it.
* **Option D:** Demeclocycline is a tetracycline antibiotic that can cause nephrogenic diabetes insipidus as a side effect, making it an inappropriate choice for treating the condition.
**Clinical Pearl / High-Yield Fact**
Desmopressin is a high-yield fact for the exam because it is a specific treatment for neurogenic diabetes insipidus, and its mechanism of action is distinct from other vasopressin analogues.
**Correct Answer:** D. Demeclocycline