Osmotic Demyelination Syndrome Resulting from an Unexpected Response to Tolvaptan in a Patient with Heart Failure

Hyponatremia is commonly encountered in patients with heart failure and has a poor prognosis.Tolvaptan, a novel selective vasopressin V2 receptor blocker, has received attention as an effective drug for treating the syndrome of inappropriate antidiuretic hormone secretion and hypervolemic hyponatremia.However, the safety of tolvaptan in the treatment of hyponatremia is not clear.We experienced a 78-year-old woman with a history of heart failure, atrial fibrillation, and hyponatremia who developed osmotic demyelination syndrome as an unexpected response to treatment with tolvaptan.(Korean J Med 2017;92:62-65)