Hyponatremia Etiology and Tolvaptan: Are we Optimally Targeting the Mechanism?

Abstract

Hyponatremia is associated with increased morbidity and mortality. Water restriction is usually the prescribed treatment for most forms of asymptomatic hyponatremia. An oral vasopressin V2-receptor antagonist, tolvaptan has been successfully used in the treatment of asymptomatic hyponatremia. In this retrospective study, tolvaptan (n=40) and a control group (n=40) were compared for asymptomatic hyponatremia etiology and response to treatment. The syndrome of inappropriate anti-diuretic hormone (SIADH) and congestive heart failure (CHF) were the most common causes of asymptomatic hyponatremia that were treated with tolvaptan. Of note, the cause of hyponatremia was not clarified in 50% of the control and 10% of the tolvaptan group. In the tolvaptan group, serum sodium concentration increased from 125±4.2 to 136±2.1 mEq/L (mean±SD, P<0.001) over 5±2 days while the control group did not show any change from its baseline value of 129.9±3 vs 128±4 mEq/L. SIADH and CHF were the most common disorders associated with asymptomatic hyponatremia and treated with tolvaptan. Importantly, 50% of the asymptomatic hyponatremia patients in the control group were labeled as unclear etiology and did not receive tolvaptan. Increased awareness of the etiology and mechanisms of asymptomatic hyponatremia development can identify individuals who benefit from tolvaptan therapy.