Severe Symptomatic Hyponatremia Induced by Trimethoprim-Sulfamethoxazole

Maria Jose Velasco


Trimethoprim-sulfamethoxazole (TMP-SMX) is a fixed-dose antimicrobial agent used in a variety of infections. Hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone is an uncommon complication of treatment with TMP-SMX. The risk seems to be higher in patients with AIDS, elderly and concomitant use of diuretics. An 88-year-old female was admitted to the hospital because of malaise and progressive confusion, 3 days after starting TMP-SMX for urinary tract infection. On physical examination the patient was euvolemic and had no evidence of malignancy, renal, cardiac, adrenal, hepatic or thyroid disease. Laboratory tests results revealed hyponatremia, low serum osmolality, urine hyperosmolarity and an elevated urine sodium concentration, leading to the diagnosis of inappropriate secretion of antidiuretic hormone. TMP-SMX was discontinued and fluid restriction was instituted. The patient was discharged after serum sodium increased from 124 mmol/L to 134 mmol/L. Two weeks after discharge the patient denied any malaise or confusion. TMP-SMX is very popular among elderly that presents with UTI. This paper is the first to emphasize this complication and the need of greater awareness among elderly population and suggest the sodium serum levels should be monitored closely during therapy with TMP-SMX.

J Med Cases. 2014;5(5):283-284


Trimethoprim-sulfamethoxazole; Syndrome; Inadequate ADH secretion

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