Diagnosis and management of hyponatremia in cancer patients.

BACKGROUND: Hyponatremia is among the metabolic disturbances encountered in oncology. Risk factors for hyponatremia include chemotherapy, treatment-induced nausea and vomiting, hydration, pain, narcotic drugs, and physical and emotional stress. A common cause of hyponatremia in patients with cancer is the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), which may result from ectopic production of arginine vasopressin (AVP) by the tumor tissue. TREATMENT: The AVP-receptor antagonists, a new class of agents, correct hyponatremia by directly blocking the binding of AVP with its receptors. In clinical trials, conivaptan, lixivaptan, tolvaptan, and satavaptan have increased serum osmolality and normalized the serum [Na(+)] in hyponatremia associated with SIADH, cirrhosis, or congestive heart failure. These drugs may have a potential in cancer-related hyponatremia as well.