[Effects of demeclocycline on psychiatric polydipsia in schizophrenic patients]

Excess intake of water by schizophrenic patients is referred to as psychiatric polydipsia. This symptom causes incontinence, vomiting and hyponatremia, and may sometimes lead to death. We have no effective therapeutic methods other than administrating sodium chloride solution and diuretics, or restricting the intake itself. A case was reported stating that demeclocycline, used in case where there is the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), was effective for the treatment of psychiatric polydipsia. We administered demeclocycline to 8 schizophrenic patients with psychiatric polydipsia, and noticed improvement in incontinence, vomiting and hyponatremia. There was also a decrease of polydipsic behavior. Demeclocycline inhibits the antidiuretic effect of vasopressin on the distal renal tubule. Considering the function of demeclocycline and the relevance of vasopressin to the central nervous system, it has been suggested that demeclocycline has effects on the central nerve through vasopressin or cyclic AMP.