The FDA ( Food and Drug Administration ) has approved Samsca tablets ( Tolvaptan ) to treat hyponatremia associated with congestive heart failure, liver cirrhosis, and the syndrome of inappropriate antidiuretic hormone secretion.

When sodium levels drop in the fluid outside of cells throughout the body, water moves into cells to balance the sodium levels and causes the cells to swell. Swelling of the brain cells is thought to cause many of the symptoms of hyponatremia. Those symptoms may include fatigue, weakness, headache, nausea, confusion or decreased consciousness, and convulsions. Severe hyponatremia, which has not been studied with Samsca, can lead to coma and death.

Samsca helps raise sodium levels in the blood by removing extra body water in the urine. Patients using the drug in clinical trials had a greater degree of increase in sodium levels in the blood compared with patients taking placebo.

Samsca is being approved with a boxed warning to alert health care professionals and patients that the drug should be started only in a hospital where blood sodium can be monitored closely. Too rapid a rise in sodium can cause a serious condition called osmotic demyelination syndrome ( ODS ).
The osmotic demyelination syndrome can lead to coma or death and can also cause symptoms such as trouble speaking, trouble swallowing, drowsiness, confusion, mood changes, seizures and trouble controlling body movement with muscle weakness in the arms and legs.

Although no cases of ODS were seen in clinical trials of Samsca, osmotic demyelination syndrome is a known risk and it is essential that physicians be aware of it and avoid rapid rises in sodium.

The most common adverse reactions with use of Samsca reported by patients in clinical trials include thirst, dry mouth, weakness, constipation, making large amounts of urine, urinating often, and increased blood sugar levels.

Source: FDA, 2009

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