Escitalopram-Induced Chronic Euvolemic Hyponatremia

Selective serotonin reuptake inhibitors (SSRIs), through the recent years have seen an increase in the number of prescriptions for a spectrum of mood disorders, especially in the geriatric population. Despite being a well-tolerated antidepressant, SSRIs have been associated with hyponatremia, a rare, but fatal adverse effect and the incidence ranges from 0.5%–32% in literature. Euvolemic hyponatremia is most commonly associated with syndrome of inappropriate secretion of antidiuretic hormone. An extensive review of literature was carried out, and we came across a total of 20 cases where escitalopram was reported as the causative agent of hyponatremia. We report a case of an 82-year-old female patient who had a history of acute onset, progressive memory impairment, and behavioral changes with depressive cognition precipitated by the death of her husband, for which she was treated with escitalopram 5 mg/day and clonazepam 0.5 mg/day. She was admitted to the hospital with presenting complaints of gait imbalance, tremors, irritability, confusion, decreased speech output and persecutory delusions. She was diagnosed with late-onset organic psychosis, precipitated and worsened by escitalopram-induced chronic uncontrolled euvolemic hyponatremia, with a sodium level of 115 mmol/L. On discontinuation of escitalopram, the patient's serum sodium level improved gradually, and her consciousness became better. This is the second case with recurrent hyponatremia in the literature up to this date, with the other being reported by Tsai et al., in 2012. Furthermore, the dose of escitalopram was only 5 mg/day compared to other reported cases where the dose ranged between 10–20 mg/day.