Tolvaptan also known as OPC-41061, is a selective, competitive

Competitive antagonist

A competitive antagonist is a receptor antagonist that binds to a receptor but does not activate the receptor. The antagonist will compete with available agonist for receptor binding sites on the same receptor...

 vasopressin receptor 2 antagonist

Vasopressin receptor antagonist

A vasopressin receptor antagonist is an agent which interferes with action at the vasopressin receptors. They can be used in the treatment of hyponatremia, especially in patients with congestive heart failure or liver cirrhosis.-Tetracyclines:...

 used to treat hyponatremia

Hyponatremia

Hyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...

 (low blood sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 levels) associated with congestive heart failure, cirrhosis

Cirrhosis

Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...

, and the syndrome of inappropriate antidiuretic hormone

Syndrome of inappropriate antidiuretic hormone

The syndrome of inappropriate antidiuretic hormone hypersecretion is characterized by excessive release of antidiuretic hormone from the posterior pituitary gland or another source. The result is hyponatremia and sometimes fluid overload...

 (SIADH). Tolvaptan was approved by the U.S. Food and Drug Administration on May 19, 2009, and is sold by Otsuka Pharmaceutical Co.

Otsuka Pharmaceutical Co.

, abbreviated OPC, is a pharmaceutical company headquartered in Tokyo, Osaka and Naruto, Japan. The company was established August 10, 1964, and currently has approximately 27,000 employees worldwide. The company focuses on pharmaceuticals related to nutrition...

 under the trade name Samsca.

Tolvaptan is also in fast-track clinical trials for polycystic kidney disease

Polycystic kidney disease

Autosomal dominant polycystic kidney disease is an inherited systemic disorder that predominantly affects the kidneys, but may affect other organs including the liver, pancreas, brain, and arterial blood vessels...

. In a 2004 trial, tolvaptan, when administered with traditional diuretic

Diuretic

A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...

s, was noted to increase excretion of excess fluids and improve blood sodium levels in patients with heart failure without producing side effects such as hypotension

Hypotension

In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

 (low blood pressure) or hypokalemia

Hypokalemia

Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...

(decreased blood levels of potassium) and without having an adverse effect on kidney function.