Psychotropic drugs, as well as some psychiatric disorders, can produce neurotoxic and life-threatening abnormalities of water and electrolyte balance that require prompt and appropriate medical intervention. Compulsive fluid intake by psychotic patients (primary polydipsia) can produce delirium due to water intoxication with hyponatremia. Several psychotropic drugs cause water retention by decreasing renal clearance, as in the syndrome of inappropriate antidiuretic hormone secretion. Lithium and other agents interfere with renal resorption of water to cause nephrogenic diabetes insipidus. Clinical signs In these disorders range from lethargy and confusion to stupor, seizures, coma, and death. This overview provides a conceptual framework for differentiating among and safely managing these relatively common disorders.