Introduction: Selective serotonin reuptake inhibitors (SSRI) are the most common antidepressants prescribed for elderly people. Although they are generally better tolerated than other antidepressant treatment classes, they can be responsible for potentially life-threatening hyponatremia, related to syndrome of inappropriate antidiuretic hormone secretion (SIADH).
Observation: A 64 years-old woman was hospitalized for cognitive function alteration and vomiting after introduction of paroxetine for depressive symptoms. Serum investigations revealed hyponatremia (121 mmol/l) with low plasma osmolarity and normal natriuria consistent with diagnosis of SIADH. Hyponatremia was reversible after paroxetine withdrawal.
Discussion: Hyponatremia induced by SIADH is a serious but underestimated complication of SSRI treatment. This complication occurs in the elderly people within the first month of treatment. Monitoring of the serum sodium concentration during the first month of treatment is recommended for older patients.