Tolvaptan, an oral, selective
arginine vasopressin (AVP)
V2 receptor antagonist has been approved for the treatment of euvolemic and hypervolemic
hyponatremia in the United States. This report summarizes our center's experience with thirteen patients treated for
hyponatremia with one 15-mg dose of
tolvaptan. The patients had euvolemic or hypervolemic
hyponatremia with decreased serum osmolality and serum
sodium (SNa) levels less than 129 mEq/L. Eight patients had a diagnosis of the syndrome of inappropriate
antidiuretic hormone (
SIADH), and five patients had a diagnosis of
congestive heart failure (CHF). Results revealed an increase in SNa in all patients from 122.5 ± 4.2 to 128.9 ± 4.1 mEq/L (P < 0.05). The mean increase in SNa of 6.4 mEq/L (range 2-10 mEq/L) 24 h post-
tolvaptan was not different in the two groups of patients, but
SIADH patients had higher pre and post-
tolvaptan SNa levels than CHF patients. Urine osmolalities (UOsm) decreased in all patients, and the patients with
SIADH had significantly higher baseline UOsm and a larger decrease in UOsm 12 h post-
tolvaptan administration when compared with the CHF patients. AVP levels did not change post-
tolvaptan administration. However, the magnitude of increase in SNa levels was inversely related to pretolvaptan AVP levels in the
SIADH subgroup (r = -0.7, P = 0.01). Three
SIADH patients received small amounts of D5W to attenuate changes in SNa. No significant changes in mean arterial pressure, serum
potassium, serum
glucose, and blood
urea nitrogen or serum
creatinine were observed. The data show that
tolvaptan is effective for the treatment of
hyponatremia and may produce differing responses in disparate patient groups.