We report an 82-year old man prescribed
paroxetine who had
hyponatremia and in whom the syndrome of inappropriate secretion of
antidiuretic hormone was diagnosed. He had taken
sulpiride for depressed mental status. However, he showed
parkinsonism, which was an adverse effect from the treatment of
sulpiride. Therefore
sulpiride was changed to
selective serotonin reuptake inhibitor,
paroxetine 10mg daily. His depressed mental status deteriorated after
paroxetine treatment started. His depression had not lessened after 12 days, and the dosage was increased to 20mg daily. On the 15th day after starting
paroxetine, routine laboratory tests showed that his serum
sodium level was 126 mEq/l. We recognized that his
confusion and loss of appetite were symptoms of
hyponatremia, rather than of worsening depression. Laboratory data revealed
hyponatremia, low serum osmolarity (242 mOsm/kg) with a relatively high level of serum
antidiuretic hormone, and concentrated urine (439 mOsm/kg). We diagnosed the syndrome of inappropriate secretion of
antidiuretic hormone (
SIADH), associated with
paroxetine. The dosage of
paroxetine was reduced gradually and the serum
sodium level returned to normal on day 2 after medication ceased completely.
Paroxetine produces fewer adverse effects than other types of
antidepressants. However, its use can be associated with inappropriate secretion of
antidiuretic hormone in the body and may lead to
SIADH, which is characterized by
hyponatremia, a potentially fatal condition that is typically asymptomatic until it becomes severe.
SIADH is more likely in some populations, including the elderly. Serum
sodium levels should be monitored closely, especially in elderly patients.