Phase I Phase II clinical trials have demonstrated that lixivaptan may play an important role in treating hyponatremia and the signs and symptoms of water retention associated with HF, liver cirrhosis with ascites (LCWA) and syndrome of inappropriate antidiuretic hormone (SIADH). Lixivaptan was previously evaluated in disease states characterized by hyponatremia with euvolemia (SIADH)and hyponatremia combined with fluid overload (HF, LCWA). Lixivaptan resulted in correction in hyponatremia together with a marked aquaresis in subject with volume overload. The present study is designed to confirm and extend the observation from previous studies that lixivaptan therapy corrects hyponatremia, in euvolemic subject, including subjects with SIDH.