Hyponatremia: an update on current pharmacotherapy.

BACKGROUND

Hyponatremia is the most common electrolyte disorder in clinical practice, and it is associated with adverse outcomes. Severe hyponatremia can result in cerebral edema and hypoxia. Moreover, even mild hyponatremia can lead to gait instability and cognitive dysfunction, especially in the elderly. The main cause of hyponatremia is nonosmotic secretion of arginine vasopressin with resultant electrolyte-free water retention. Thus, the available management for chronic hyponatremia must increase solute-free water excretion, such as occurs with blocking vasopressin receptors with selective V2 antagonists.

METHODS

Several recent trials have assessed the efficacy and safety of hyponatremia treatment using vasopressin receptor antagonists (vaptans). These trials documented the efficacy of vaptans to reverse hyponatremia. Moreover, treatment of hypervolemic hyponatremia, such as in heart failure or liver cirrhosis, with vasopressin receptor antagonist results in increased solute-free excretion without activation of the neurohumoral systems. The current review covers results on management of hyponatremia with different vasopressin receptor antagonists.

CONCLUSIONS

Approaches, such as vasopressin receptor antagonists or urea, have been shown to reverse moderate hyponatremia. However, these agents have not been used to treat severe hyponatremia in clinical trials. Future studies in severe hyponatremic states are required to assess the impact of vaptans on clinically significant end points, such as morbidity and mortality.