The treatment of
hyponatremia, especially euvolemic and hypervolemic
hyponatremia, has changed with the development of drugs which function as
vasopressin receptor antagonists. These agents increase solute-free water excretion by the kidney resulting in an aquaresis.
Conivaptan, a
vasopressin receptor antagonist, has recently been approved by the FDA in the United States for use in the
therapy of both euvolemic and hypervolemic
hyponatremia. This report summarizes one center's experience with ten patients treated with this new
drug. The patients had euvolemic
hyponatremia with serum
sodium levels less than 128 mEq/l. The same protocol was used in all patients with the
conivaptan being given as a 20-mg intravenous loading dose followed by a 20-mg continuous 24-h infusion. Review of the data revealed that six of the ten patients had an excellent response to the
therapy, with serum
sodium increasing by a mean of 8.5+/-0.8 mEq/l (increases ranged from 7 to 12 mEq/l over 24 h). No significant changes in serum
potassium levels or mean arterial pressures were noted. Two of the ten patients experienced a decrease in urine osmolality without a significant increase in serum
sodium. Two other patients had only slight decreases in urine osmolality, and no significant increase in serum
sodium levels. The data reveal that
conivaptan is useful in the management of significant
hyponatremia. There were no significant untoward effects, with the exception of one patient whose blood pressure decreased during the
conivaptan infusion and who responded to cessation of the infusion and saline replacement
therapy. This new class of drugs holds great promise for the treatment of dilutional hyponatremic disorders.