Tolvaptan

Tolvaptan (INN), also known as OPC-41061, is a selective, competitive arginine vasopressin receptor 2 antagonist used to treat hyponatremia (low blood sodium levels) associated with congestive heart failure, cirrhosis, and the syndrome of inappropriate antidiuretic hormone (SIADH). Tolvaptan was approved by the U.S. Food and Drug Administration on May 19, 2009, and is sold by Otsuka Pharmaceutical Co. under the trade name Samsca.

Tolvaptan is also in fast-track clinical trials for polycystic kidney disease. In a 2004 trial, tolvaptan, when administered with traditional diuretics, 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 (low blood pressure) or hypokalemia (decreased blood levels of potassium) and without having an adverse effect on kidney function.

Chemistry
Chemical synthesis: