LAUSR

Background: Trimethoprim-sulfamethoxazole (TMP/SMX) causes hyperkalemia, and hyponatremia caused by TMP/SMX is a challenge for clinicians. We described the clinical features of hyponatremia induced by TMP/SMX after collecting cases. Summary: The median age of the 24 patients (10 males and 14 females) was 67 years (range: 28–90 years). Hyponatremia induced by TMP/SMX manifested as nausea (41.7%) and vomiting (29.2%) or asymptomatic hyponatremia (20.8%). The median duration of hyponatremia was 5 days (range: 3–10 days). The median serum sodium concentration was 118 mmol/L (range: 101–128.1 mmol/L). The serum sodium levels gradually returned to the normal range at 4 days (median; range: 2–14 days) after withdrawing TMP/SMX. Key Messages: TMP/SMX-induced hyponatremia is a rare and serious adverse reaction. Clinicians should be aware of electrolyte disturbances caused by TMP/SMX and should always consider electrolyte monitoring.