Successful treatment of hypernatremic thirst deficiency with chlorpropamide

Two patients with hypodipsia and hypernatremia are described. The first patient, whose hypodipsia was of unknown cause, developed hypernatremia unless large volumes of fluid were urged upon him; upon treatment with chlorpropamide normal serum sodium levels were achieved with spontaneous fluid intake. The second patient had hypodipsia and diabetes insipidus resulting from a craniopharyngioma. Treatment with vasopressin and a prescribed daily water intake resulted in frequent hyper- and hyponatremia, but treatment with chlorpropramide yielded serum sodium values which were more often normal and less variable. In neither patient could the improved water regulation be attributed to an effect of chlorpropamide on renal water excretion. Possible mechanisms for the effect of chlorpropamide on thirst are discussed.