Clozapine reduces water-drinking behavior in schizophrenic patients with polydipsia

Disordered water balance, or polydipsia, is an underassessed and underreported phenomenon present in the severely psychiatrically disabled population. Prevalence rates for polydipsia range from 6.2 to 20%. We followed up five male patients (mean age 43) with chronic schizophrenia who met the Kane criteria for being treatment nonresponders and who, in addition, had marked polydipsia. Three patients had previously received medical care for hyponatremia and had to be placed on fluid restriction when admitted to the hospital. All patients exhibited polydipsia despite high doses of typical antipsychotic drugs. Each patient was treated openly with clozapine (range 450-800 mg/day) for at least 6 months. In each case, there was a decline in the Brief Psychiatric Rating Scale score (preclozapine mean, 63; postclozapine mean, 46), and a marked reduction in fluid-seeking behavior. All fluid restrictions could be lifted, and the patients were discharged from the hospital. During a mean follow-up period of 17 months, during which patients were evaluated weekly, polydipsic behavior that required intervention had not been noted. We conclude that clozapine may be a highly effective treatment for polydipsia in patients with treatment-refractory schizophrenia. Future studies may aim to delineate neurobiologic mechanisms.