Astellas Pharma US, Inc. has received an approval from the US Food and Drug Administration for Vaprisol (conivaptan hydrochloride injection), an arginine vasopressin (AVP) antagonist for the intravenous treatment of euvolemic hyponatremia in hospitalised patients.

Vaprisol, discovered and developed by Astellas, is the first drug specifically indicated for the treatment of euvolemic hyponatremia, a potentially life- threatening condition that occurs when the body's blood sodium level falls significantly below normal. The FDA also issued an approvable letter for Vaprisol as a treatment for hypervolemic hyponatremia. Astellas plans on working closely with the FDA to obtain an approval for Vaprisol's use in patients with hypervolemic hyponatremia, states a company release.

"Vaprisol will provide physicians with an important new treatment option for a serious condition. The approval of Vaprisol further illustrates Astellas' commitment to developing innovative pharmaceutical products that improve healthcare," said Makoto Nishimura, president and chief executive officer of Astellas Pharma US, Inc.

In a randomised, double-blind, placebo-controlled study, intravenous administration of Vaprisol 40 mg/day for four days corrected the balance of sodium and water in hospitalised patients with mild to moderate euvolemic hyponatremia. Significant improvements in serum sodium levels were observed within the first day of treatment with Vaprisol. The most common adverse events associated with Vaprisol were infusion site reactions, most of which were mild and did not lead to discontinuation of the drug.

"Currently available treatment options for hyponatremia, such as fluid restriction, diuretics and saline solution are inconsistent in their effects. Vaprisol will allow us to effectively correct the sodium-water balance in patients with euvolemic hyponatremia, and will help us to better manage this common and potentially very serious condition," said Joseph Verbalis, chair, department of medicine, Georgetown University Medical Centre.

Hyponatremia often results from elevated levels of the hormone arginine vasopressin (AVP), which regulates water and salt balance in the body. It is the most common electrolyte disorder in clinical medicine and one of the most difficult to treat. Hyponatremia is estimated to affect up to 4 per cent of hospitalised patients in the United States each year.

Vaprisol is a novel drug that blocks the activity of AVP, resulting in increased urine output without loss of valuable electrolytes such as sodium and potassium.

Astellas Pharma US, Inc., a US subsidiary of Tokyo-based Astellas Pharma Inc., is a research-based pharmaceutical company dedicated to improving the health of people around the world through the provision of innovative and reliable pharmaceutical products.