ABSTRACT
We report a severe case of hyponatremic encephalopathy in a 38 year old schizophrenic patient with polydipsia that was very likely precipitated by hydrochlorothiazide given for the accompanied hypertension in this patient. On admission via emergency room, this patient's electrolyte imbalances include not only hyponatremia but also hypokalemia, hypomagnesemia and metabolic alkalosis, which have been well known as the complications of thiazide diuretics. Fortunately, this patient recovered from comatose condition with the treatment of hyponatremia at the correction rate of about 0.5mEq/L/hr in addition to potassium and volume replacements. However, this case gives us the warning that the presence of hyponatremic condition such as polydipsia should be ruled out before thiazide diuretics prescribed for patients with schizophrenia, and other electrolytes imbalance in addition to hyponatremia as the complications of thiazide diuretics should be looked for the simultaneous treatment for them.