Wednesday April 18, 2007
(arginine vasopressin) AVP-Receptor Antagonists

Hyponatremia may be caused by a number of conditions, including infections, heart disease, surgery, malignancy, and medication use. Clinical signs and symptoms such as hallucinations, lethargy, weakness, bradycardia, respiratory depression, seizures, coma, and death have been reported. Conventional treatment consists of fluid restriction and administration of hypertonic saline and pharmacologic agents, such as demeclocycline, lithium carbonate, and urea. These treatment options are often of limited effectiveness or difficult for patients to tolerate.

AVP (arginine vasopressin) promotes the reabsorption of water in the renal collecting ducts by activation of V2 receptors, resulting in water retention and dilution of serum solutes. The AVP-receptor antagonists, Conivaptan, Lixivaptan, and Tolvaptan, are being studied for the treatment of hyponatremia.

Conivaptan (Vaprisol) has been shown in clinical trials to increase freewater excretion and safely normalize serum sodium concentrations in patients with hyponatremia and is well tolerated. Also in clinical trials, Lixivaptan and Tolvaptan have safely improved serum sodium concentrations in patients with hyponatremia.