Conivaptan HCl is primarily used in the treatment of euvolemic and hypervolemic hyponatremia, a condition characterized by low sodium levels in the blood with normal or increased fluid volume. It works by blocking vasopressin receptors (V1A and V2) in the kidneys, promoting the excretion of excess water without significant electrolyte loss—a process known as aquaresis. This selective action helps raise serum sodium levels in patients where fluid restriction alone is insufficient. It is commonly administered intravenously in hospital settings, especially for patients with hyponatremia associated with heart failure, liver cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). Due to its potent effect and potential for rapid sodium correction, careful monitoring is required to avoid overcorrection, which can lead to serious neurological complications.