The FDA (Food and Drug Administration) has approved Samsca (tolvaptan), in tablet form, for the treatment of hyponatremia. Hyponatremia is when levels of sodium in the blood are abnormally low - it is associated with dehydration.

Norman Stockbridge, M.D., Director, Division of Cardiovascular and Renal Products, Center for Drug Evaluation and Research, FDA, said "With the approval of Samsca, physicians will have an additional tool to treat hyponatremia."

Samsca is approved to treat hyponatremia associated with congestive heart failure, liver cirrhosis, and the syndrome of inappropriate antidiuretic hormone secretion.

When levels of sodium fall in the fluid outside of cells throughout the human body, water enters the cells to balance sodium levels - this makes the cells swell. Many symptoms of hyponatremia are thought to arise from the swelling of the brain cells, the FDA informs. Symptoms include:

* Headache
* Weakness
* Confusion
* Decreased consciousness
* Nausea

Samsca removes extra body water in the urine, thus helping raise sodium levels in the blood. In clinical trials, participants taking Samsca had higher increases in blood sodium levels compared to participants receiving a placebo (dummy drug).

The approval of Samsca includes a boxed warning that alerts doctors, pharmacists, other health care professionals, and patients that the medication should be started only in a hospital where blood sodium levels can be monitored carefully. If blood sodium levels rise to quickly there is a risk of osmotic demyelination syndrome (ODS). ODS can lead to coma, and even death. It can cause the patient to have problems speaking, swallowing, as well as causing drowsiness, confusion, mood changes, seizures, and problems controlling body movement with muscle weakness in the limbs.

Even though there were no cases of ODS detected during the clinical trials of Samsca, ODS is a known risk and it is crucial that doctors be aware of it, and make sure rapid increases in sodium levels do not occur, the FDA said. In addition, the FDA is requiring a Risk Evaluation and Mitigation Strategy that requires a patient Medication Guide be given when the drug is dispensed. The Medication Guide will have information about the risks and benefits of the drug.

During the clinical trials, the following side-effects were reported by participants: thirst, dry mouth, weakness, constipation, excessive urination, frequent urination, and raised blood sugar levels.