Vasopressin dysregulation: hyponatremia, fluid retention and congestive heart failure.

Arginine vasopressin (AVP) plays a central role in the regulation of water and electrolyte balance. Dysregulation of AVP secretion, along with stimulation of AVP V2 receptors, is responsible for hyponatremia (serum sodium concentration <135 mEq/L) in congestive heart failure (CHF). The stimulation of atrial and arterial baroreceptors in response to hypotension and volume depletion results in the nonosmotic release of AVP. The predominance of nonosmotic AVP secretion over osmotic AVP release plays a key role in the development of water imbalance and hyponatremia in CHF and other edematous disorders. The AVP-receptor antagonists are a new class of agents that block the effects of AVP directly at V2 receptors in the renal collecting ducts. AVP-receptor antagonism produces aquaresis, the electrolyte-sparing excretion of water, thereby allowing specific correction of water and sodium imbalance. This review summarizes recent data from clinical trials evaluating the efficacy and safety of these promising agents for the treatment of hyponatremia.