Which of the following is the drug of choice for the treatment of syndrome of inappropriate Antidiuretic Harmone secretion?
**Core Concept**
The syndrome of inappropriate antidiuretic hormone (SIADH) secretion is characterized by the excessive release of antidiuretic hormone (ADH), leading to water retention and hyponatremia. This results from an imbalance in the body's regulation of water and electrolytes, primarily due to an overproduction of ADH, often caused by ectopic hormone production or other pathologies.
**Why the Correct Answer is Right**
The treatment of SIADH involves correcting the underlying cause and managing the symptoms. The drug of choice for SIADH is **Vasopressin receptor antagonist, Conivaptan**. Conivaptan works by competitively inhibiting the action of vasopressin at the V2 receptors in the renal collecting duct, thereby reducing water reabsorption and increasing urine output. This action helps to correct hyponatremia and reduce water overload.
**Why Each Wrong Option is Incorrect**
**Option A:** **Demeclocycline** is a tetracycline antibiotic that can be used to treat SIADH by inducing nephrogenic diabetes insipidus, but it is not the drug of choice. It works by decreasing the responsiveness of the kidneys to ADH.
**Option B:** **Hydrochlorothiazide** is a diuretic that can worsen hyponatremia in SIADH by increasing sodium loss in the urine.
**Option C:** **Furosemide** is a loop diuretic that can also worsen hyponatremia in SIADH by increasing sodium loss in the urine.
**Clinical Pearl / High-Yield Fact**
In SIADH, it is essential to monitor sodium levels closely and correct them gradually to avoid osmotic demyelination syndrome (ODS), which can occur with rapid correction of hyponatremia.
**Correct Answer:** C. Conivaptan