Syndrome of inappropriate secretion of antidiuretic hormone associated with paroxetine

A 71-year old man with failed back syndrome was admitted to hospital with oliguria that had occurred 4 days after his dose of paroxetine had been increased to 40 mg x day(-1). Laboratory data on admission revealed hyponatremia (124 mmol x l(-1)), low serum osmolarity (267 mOsm x l(-1)) with a normal level of serum antidiuretic hormone (1.7 pg x ml(-1)), and concentrated urine (430 mOsm x l(-1)). He was diagnosed as having syndrome of inappropriate secretion of antidiuretic hormone, associated with paroxetine; this drug was discontinued immediately after admission. The hyponatremia was treated with saline infusion, water restriction, and furosemide; serum sodium level returned to normal on hospital day 5. Paroxetine is being increasingly used for depression and chronic pain management because of its favorable side-effect profile; however, we should be alert to hyponatremia in patients on paroxetine by carrying out periodic monitoring of serum electrolytes, especially in elderly patients.