Abstract: PUB089
Trimethoprim-Sulfamethoxazole-Induced Epithelial Sodium Channel (ENaC) Inhibition Mimicking Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) in a Patient with Hyponatremia, Hyperkalemia, and AKI
Session Information
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Aboelatta, Noureldin Ashraf Hassan Sabry Hassan, The University of New Mexico Hospital, Albuquerque, New Mexico, United States
- Jayeola, Olakunle A., The University of New Mexico Hospital, Albuquerque, New Mexico, United States
- Abdali, Mohamed, The University of New Mexico Hospital, Albuquerque, New Mexico, United States
Introduction
Trimethoprim sulfamethoxazole (TMP SMX) can cause electrolyte disturbances through trimethoprim mediated inhibition of epithelial sodium channels in the distal nephron. Hyponatremia from this mechanism may mimic SIADH and cerebral salt wasting because urine sodium and urine osmolality may be elevated. Reports of the full electrolyte creatinine triad are limited.
Case Description
A 67 year old man with hypertension and a right thalamic intraparenchymal hemorrhage received TMP SMX for Morganella morganii bacteremia. Five days later he developed hyponatremia (124 mmol/L), hyperkalemia (5.8 mmol/L) and a creatinine increase (0.7→1.59 mg/dL). Urine osmolality was 430 mOsm/kg, sodium 58 mmol/L and TTKG 2.9. Plasma renin activity was 19.7 ng/mL/hr, aldosterone 4.6 ng/dL. He was hypovolemic and not on RAAS inhibitors or potassium sparing agents. TMP SMX was stopped, isotonic saline and oral NaCl were given, leading to normalization of electrolytes and renal function.
Discussion
Trimethoprim behaves like amiloride, impairing sodium entry and potassium excretion, leading to natriuresis and hyperkalemia. Hypovolemia, hyperkalemia, low TTKG and a high renin low aldosterone profile supported trimethoprim induced distal nephron dysfunction. Cerebral salt wasting does not cause hyperkalemia or impaired potassium secretion, and SIADH is euvolemic. A Naranjo score of 7 indicated a probable adverse drug reaction. Recognizing that hyponatremia with hyperkalemia after TMP SMX suggests ENaC inhibition allows prompt discontinuation and resolution.