Severe Hyponatremia Secondary to Escitalopram Therapy: A Case Study

Background: Hyponatremia secondary to syndrome of inappropriate antidiuretic hormone (SIADH) secretion is a well-known complication of selective serotonin reuptake inhibitors (SSRI), however it is rarely seen with the new generation SSRIs. There have only been fifteen reported cases of hyponatremia with the newest SSRI, escitalopram. Case Presentation: A 77-year-old female was admitted to the hospital for altered mental status and hyponatremia. Her past medical history was significant for anxiety treated by escitalopram oxalate 10 mg daily. Patient reported increased weakness and use of walker due to recent history of falls. On exam, she was communicating slower than her baseline but otherwise speech, memory, and orientation seemed unchanged. Mucous membranes were dry and skin tenting was present. A diagnosis of SIADH was made based on clinical findings, laboratory findings of severe hyponatremia, hypotonicity, elevated urine osmolality, and after ruling out other causes of hyponatremia due to normal renal, adrenal, and thyroid function. Patient's SIADH was attributed to the escitalopram she was started on for anxiety fourteen days before admission. After treatment, patient was asymptomatic and discharged with a sodium level of 121 mEq/L. Repeat sodium levels were 130 mmol/L eleven days after discharge and patient was started on mirtazapine for anxiety. She has had no episodes of hyponatremia since discontinuing escitalopram. Conclusion: Physicians should be aware of SIADH development secondary to SSRIs in the elderly even with new generation SSRIs such as escitalopram. Electrolytes should be monitored regularly, especially in the first two weeks after starting the medication.