Tolvaptan Corrects Hyponatremia in Cancer Patients

November 21, 2013

By Robert Saunders

NEW YORK (Reuters Health) Nov 21 - In hospitalized cancer patients, the common problem of hyponatremia can be corrected by administration of the orally active V2 receptor antagonist, tolvaptan.

The finding comes from a relatively small double-blind placebo-controlled trial funded by Otsuka America Pharmaceuticals Inc. "This randomized trial shows that compared to placebo, tolvaptan is very effective in correcting hyponatremia in cancer patients," lead author Dr. Abdulla K. Salahudeen commented by email.

"In clinical practice, correction of hyponatremia can be difficult in some cancer patients, which can sometimes delay initiation or continuation of chemotherapy, undertaking surgery or performing stem cell transplant," he told Reuters Health. "Use of tolvaptan especially in such patients should be considered."

Dr. Salahudeen and colleagues at The University of Texas MD Anderson Cancer Center, Houston, explain in their paper in Cancer, online November 5, that while the availability of inhibitors of the V2 receptor of arginine vasopressin hormone has greatly aided the management of hyponatremia, the safety and efficacy of this approach has not been tested in patients with cancer.

The researchers therefore randomized 48 cancer patients with serum sodium levels of 125-130 mmol/L to receive tolvaptan or placebo for 14 days. The primary goal was a sodium level of 136-147 mmol/L.

Both groups received standard of care for hyponatremia, except that they were allowed to drink water to relieve thirst. This was partly because the usual practice of fluid restriction is impractical in cancer patients, and partly in order to lessen the possibility of sodium overcorrection.

Thirty patients completed the study. Hyponatremia was corrected in 16 of 17 patients given tolvaptan compared to 1 of 13 placebo patients (94% vs. 8%; p<0.001), the authors report.

In fact, they point out, "The correction in the tolvaptan group was evident from the first day of its use; the majority of patients achieved eunatremia by day 7, and nearly all achieved eunatremia by day 14."

The targeted sodium correction rate of 6-12 mmol/L per day was not exceeded in any of the tolvaptan group. The main adverse effects were dry mouth, polydipsia and polyuria, which led to a 13% withdrawal rate.

Secondary end points of length of stay and change in mental status were not significantly different between the two groups, Dr. Salahudeen and colleagues report.

"Although tolvaptan was effective for correcting hyponatremia in patients with cancer," they conclude, "studies with a larger sample size will be required to confirm the current findings, including the outcomes of secondary endpoints."

Dr. Salahudeen added, "Larger studies are being designed to evaluate whether tolvaptan-induced prompt and safe correction leads to better clinical outcomes."

SOURCE: http://bit.ly/I6Q3N5

Cancer 2013.

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