A 42-year-old man is on amitriptyline for depression. Recently he has been feeling more lethargic and unwell. His clinical examination is normal. Serum sodium is 125 mEq/L and osmolality is 260 mOsm/kg, and urine sodium is 40 mEq/L and osmolality is 450 mOsm/kg.For the above patient with hyponatremia, select the most likely diagnosis.
Amitriptyline is one of the psychoactive drugs that cause SIADH. Others include phenothiazines, serotonin reuptake inhibitors, and monoamine oxidase inhibitors (MAOIs). Antineoplastic drugs such as vincristine and cyclophosphamide also cause SIADH, as does the hypoglycemic agent chlorpropamide.
congestive heart failure (CHF)
extrarenal sodium and fluid losses
SIADH
polydipsia
Oncology