Astellas Pharma US Inc. announced that the US Food and Drug Administration (FDA) has approved Vaprisol (conivaptan hydrochloride injection), an arginine vasopressin (AVP) receptor antagonist, for the intravenous treatment of hypervolemic hyponatremia in hospitalised patients.

Vaprisol, discovered and developed by Astellas, is the first drug specifically indicated for the treatment of both euvolemic and hypervolemic hyponatremia, potentially life-threatening conditions that occur when the body's blood sodium level falls significantly below normal.

Vaprisol was approved by the FDA as a treatment for euvolemic hyponatremia in December 2005, and has been marketed by Astellas since April 2006. Hyponatremia is estimated to affect up to four per cent of hospitalised patients in the United States each year. While many patients with hyponatremia have no symptoms, severe cases are medical emergencies that can result in swelling of the brain, respiratory arrest and death.

Hypervolemic hyponatremia, which occurs when the total body water increase is greater than the body's serum sodium levels, resulting in edema (swelling of body tissues) and is often associated with congestive heart failure, severe liver disease and kidney failure.

In the treatment of hyponatremia associated with congestive heart failure, Vaprisol is indicated only for those patients for whom the expected benefit of raising serum sodium outweighs the increased risk of adverse events. Caution should be used when administering Vaprisol to patients with liver or kidney impairment.

"With this additional indication, Vaprisol will provide physicians with an important new treatment option for patients with this often serious condition," said Yoshihiko Hatanaka, CEO at Astellas Pharma US, Inc. "Astellas is committed to developing novel treatments and providing innovative products such as Vaprisol in order to solidify its presence in the critical care market."

In a randomised, double-blind, placebo-controlled study, intravenous administration of Vaprisol 40 mg/day for four days achieved a clinically meaningful aquaresis, which resulted in increased serum sodium levels in hospitalised patients with hypervolemic hyponatremia. Aquaresis is defined as the excretion of electrolytefree water. Significant increases in serum sodium levels were observed within the first day of treatment with Vaprisol (mean increase of 6.4 mEq/L at 24 hours) and continued throughout the remainder of the treatment period. The most common adverse events associated with Vaprisol were infusion-site reactions.

Some serious infusion-site reactions did occur, however, these were the most common types of adverse events leading to the discontinuation of Vaprisol.
"Vaprisol is the first dual V1a and V2 vasopressin receptor antagonist approved by the FDA for the treatment of hypervolemic and euvolemic hyponatremia," said Steven R. Goldsmith, MD, Professor of Medicine at the University of Minnesota Medical School. "Vaprisol is a novel treatment option that effectively increases serum sodium levels and will help physicians to manage these potentially very serious conditions."