Novel Drug Treats Low Blood Sodium
Experimental Drug May Help Heart Failure, Cirrhosis, and Other Patients
Nov. 16, 2006 - An experimental drug helps normalize low blood sodium levels
in people with heart failure, cirrhosis, and other conditions.
The oral drug is tolvaptan. It's designed to allow for the removal of plain
water through the urine.
If the sodium level in the blood is low, people get a condition known as
hyponatremia. Low blood sodium has been linked to increased complications and
death in people with heart failure, liver cirrhosis, and other conditions.
Sodium is an essential chemical element that affects the function of cells
all over the body.
University of Colorado researcher Robert W. Schrier, MD, and colleagues
conducted two clinical trials of tolvaptan in people with low blood sodium due
to heart failure, cirrhosis, and other conditions. All of the patients were
treated outside the hospital.
In the studies, tolvaptan's positive effects became apparent after four days
of treatment. After 30 days of treatment, more than half of the patients
getting tolvaptan had normal blood sodium levels. Only a fourth of patients who
got inactive placebo pills had normal blood sodium levels after 30 days.
After 30 days, 7% of tolvaptan patients in one study and 15% of tolvaptan
patients in the other study had seriously low blood sodium levels. Seriously
low blood sodium levels occurred in 35% and 32% of placebo-treated
Side effects of tolvaptan included thirst, dry mouth, and increased
urination. More serious side effects -- seen in patients receiving tolvaptan as
well as in those receiving the placebo -- included low blood pressure, dizziness, and
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 New
England Journal of Medicine. In an editorial accompanying the report, Richard
M. Hays, MD, of New York's Albert Einstein College of Medicine, warns that
patients taking tolvaptan must be watched closely.
"It is clear that careful oversight of the use of this agent is
required, not only by means of frequent clinic visits and measurement of [blood
sodium levels], but also through daily measurement of body weight by
patients," Hays suggests.