Chronic hyponatremia

This study is examining how a dietary supplement called urea can be used to treat low blood sodium level. Low blood sodium level is a common problem and some studies show that many patients with low blood sodium level suffer from brain fog and/or loss of balance. Unfortunately, it is unknown at this point what the best treatment is for low blood sodium level. With this pilot research study, the investigators are hoping to learn more about whether urea is safe to take, whether patients can tolerate taking urea for several weeks, whether urea increases blood sodium level, and whether urea can help prevent the brain fog and/or loss of balance that some patients with low blood sodium level suffer from. The information obtained with this study is intended to be used to design a larger study in the future to get a definite answer whether urea is beneficial for patients with low blood sodium level.

To evaluate the overall safety and continued efficacy of oral lixivaptan capsules in subjects with euvolemic and hypervolemic hyponatremia

To demonstrate that after 12 weeks of open-label lixivaptan treatment, serum sodium is maintained in hyponatremic patients continuing to receive lixivaptan compared to placebo during the 4 week double blind treatment period.