Clinical review: the use of vaptans in clinical endocrinology.

CONTEXT: Hyponatremia is the most common electrolyte disorder encountered in clinical practice and represents a clinical, social, and economic burden. Conventional treatments of hyponatremia present some pitfalls, such as suboptimal efficacy, risk of overly rapid correction, and adverse effects. Vasopressin receptor antagonists, known as vaptans, represent a new and interesting class of drugs for the treatment of the euvolemic and hypervolemic forms of hyponatremia. EVIDENCE ACQUISITION: This review is based on a PubMed search with the following terms: "vaptans," "vasopressin receptor antagonists," "tolvaptan," "conivaptan," "vasopressin receptor antagonists and SIADH," "vasopressin receptor antagonists and congestive heart failure," "vasopressin receptor antagonists and cirrhosis," and "vasopressin receptor antagonists and polycystic kidney disease." EVIDENCE SYNTHESIS: Overall, the studies reported in this review indicate that vaptans effectively correct hyponatremia in euvolemic and hypervolemic patients. In the latter group, vaptans generally had favorable effects on fluid balance also. To date two vaptans, ie, conivaptan and tolvaptan, have been marketed in the United States for the treatment of euvolemic and hypervolemic hyponatremia, whereas tolvaptan has been marketed in Europe with the limitation of euvolemic hyponatremia. Although these drugs have a good safety profile, caution should be used, and treatment should be initiated in a hospital setting in order to closely monitor patients and avoid overly rapid correction or overcorrection.
CONCLUSIONS: Vaptans can be considered a new effective tool for the treatment of euvolemic and hypervolemic hyponatremia. Nevertheless, more comparative research of vaptans vs other therapies on clinical grounds is needed to more accurately assess the value of these drugs in the treatment of hyponatremia.