Citalopram-associated SIADH

OBJECTIVE: To report a case of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with use of citalopram in an elderly male patient and to review the English-language literature for any previous reports of SIADH or hyponatremia caused by citalopram. CASE SUMMARY: An 87-year-old Filipino man was admitted to the hospital reporting malaise, confusion, dizziness, and falls approximately 3 weeks following an increase in his citalopram dosage from 10 to 20 mg/d. On physical examination, the patient was euvolemic and had no evidence of malignancy, cardiac, renal, or hepatic disease. Pertinent laboratory test results revealed hyponatremia, serum hypoosmolality, urine hyperosmolality, and elevated urine sodium concentration, leading to a diagnosis of SIADH. Citalopram was discontinued and fluid restrictions were instituted. The patient was discharged after his serum sodium increased from 122 to 128 mEq/L and he reported increased strength and decreased confusion. Five days after discharge, the patient denied experiencing any new falls, weakness, confusion, or lethargy. His serum sodium measured that day was 131 mEq/L; 2 months later, it was 135 mEq/L. DISCUSSION: We report the seventh case of citalopram-induced hyponatremia published in the English language and the second in a man. Review of the cases demonstrated that the onset of citalopram-induced hyponatremia or SIADH ranged from 6 to 20 days. Potential risk factors for SIADH due to citalopram included advanced age, female gender, concomitant use of medications known to cause SIADH or hyponatremia, and, possibly, higher citalopram doses. CONCLUSIONS: Elderly patients receiving citalopram should be monitored for signs and symptoms of SIADH, especially in the first few weeks of therapy, in the presence of risk factors, and during dose escalation.