To the Editor: It is estimated that 10%–25% of patients with chronic schizophrenia develop polydipsia (1–4). One-third become hyponatremic. Seizures, coma, and death may occur when sodium levels fall below 120 mmol/liter (1). It is unclear why these patients develop polydipsia; one possibility is that enlargement of the ventricles impairs their baroreceptors.
Mr. A, a 56-year-old single white man with a 40-year history of chronic schizophrenia, was being treated with standard and atypical neuroleptics. He lived with his elderly mother. He had had two life-threatening episodes of hyponatremia-induced coma and was incapable of stopping his polydipsia. Mr. A was encouraged to drink only an electrolyte-balanced sports drink and also to take one salt pill with each meal.
Urinary frequency and enuresis were first noted. Later, seizures and a coma resulted in hospitalization, and a diagnosis of hyponatremia and rhabdomyolysis was made. His electrolyte level was stabilized, and he was then transferred to a psychiatric hospital. Other causes of hyponatremia, including the syndrome of inappropriate antidiuretic hormone secretion, renal disease, and Addison’s disease, were ruled out. A computerized tomography scan suggested a stroke involving the caudate nucleus and generalized cerebral atrophy. Mr. A’s sodium level fluctuated from 137 to 142 mmol/liter. He was discharged taking clozapine, olanzapine, and sertraline.
Recurrence of seizures resulted in rehospitalization. During Mr. A’s second hospitalization, his serum sodium level fluctuated from 127 to 147 mmol/liter (four measurements were between 127 and 129 mmol/liter). Hospital treatment included behavior therapy, propranolol, fluoxetine, and olanzapine, but none of these benefited him (2).
One month after discharge, Mr. A’s sodium levels were still below normal (127 mmol/liter) and appeared to be life threatening. He did not understand the importance of limiting fluid intake. His elderly mother was unable to monitor his drinking. Mr. A’s fluid intake was limited to an electrolyte-balanced sports drink. He took one 19-mg salt pill with each meal. In the past year, his sodium levels have been normal, there have been no seizures, and his mental status has improved.
At the time this treatment was initiated, hyponatremia, coma, and death appeared possible. Use of previously recommended behavioral and pharmacological treatments were unsuccessful (1–4). While water restriction of a delusional polydipsic patient outside a hospital may not be feasible, an electrolyte-balanced solution may be lifesaving. This anecdotal observation requires replication. Of note is that this patient’s mental status improved, as evidenced by enhanced orientation, with stabilized sodium levels.