Successful mirtazapine treatment of an 81-year-old patient with syndrome of inappropriate antidiuretic hormone secretion.

Elderly patients are at a higher risk for inappropriate antidiuretic hormone secretion when treated with antidepressants. In response to severe depressive symptoms, we initiated treatment with citalopram of an 81-year-old female patient with slightly reduced sodium and chloride levels. The sodium and chloride levels decreased continuously during treatment with citalopram; six days after the citalopram was discontinued, sodium and chloride levels returned to normal. We then switched treatment to mirtazapine. Close monitoring revealed that the patient's sodium and chloride levels never decreased and the patient did not relapse for more than two months. This case study indicates that treatment with citalopram may worsen preexisting hyponatremia. Mirtazapine appears to be safe for use in high-risk, elderly patients.