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Novel Drug Treats Low Blood Sodium

Experimental Drug May Help Heart Failure, Cirrhosis, and Other Patients

Medically Reviewed by Louise Chang, MD on November 16, 2006
From the WebMD Archives

Nov. 16, 2006 - An experimental drug helps normalize low blood sodium levelsin people with heart failure, cirrhosis, and other conditions.

The oral drug is tolvaptan. It's designed to allow for the removal of plainwater through the urine.

If the sodium level in the blood is low, people get a condition known ashyponatremia. Low blood sodium has been linked to increased complications anddeath in people with heart failure, liver cirrhosis, and other conditions.

Sodium is an essential chemical element that affects the function of cellsall over the body.

University of Colorado researcher Robert W. Schrier, MD, and colleaguesconducted two clinical trials of tolvaptan in people with low blood sodium dueto heart failure, cirrhosis, and other conditions. All of the patients weretreated outside the hospital.

In the studies, tolvaptan's positive effects became apparent after four daysof treatment. After 30 days of treatment, more than half of the patientsgetting tolvaptan had normal blood sodium levels. Only a fourth of patients whogot inactive placebo pills had normal blood sodium levels after 30 days.

After 30 days, 7% of tolvaptan patients in one study and 15% of tolvaptanpatients in the other study had seriously low blood sodium levels. Seriouslylow blood sodium levels occurred in 35% and 32% of placebo-treatedpatients.

Side effects of tolvaptan included thirst, dry mouth, and increasedurination. More serious side effects -- seen in patients receiving tolvaptan aswell as in those receiving the placebo -- included low blood pressure, dizziness, andfainting.

The number of deaths was similar in the tolvaptan and placebo groups.

Schrier and colleagues report the findings in the Nov. 16 issue of The NewEngland Journal of Medicine. In an editorial accompanying the report, RichardM. Hays, MD, of New York's Albert Einstein College of Medicine, warns thatpatients taking tolvaptan must be watched closely.

"It is clear that careful oversight of the use of this agent isrequired, not only by means of frequent clinic visits and measurement of [bloodsodium levels], but also through daily measurement of body weight bypatients," Hays suggests.

Show Sources

SOURCES: Schrier, R.W. The New England Journal of Medicine, Nov. 16, 2006; vol 355: pp 2099-2112. Hays, R.M. The New England Journal of Medicine, Nov. 16, 2006; vol 355: pp 2146-2148. News release, Otsuka America Pharmaceuticals Inc.

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