Pharmacy Phriday #7: Bactrim Adverse Events - The Emergency Medical Minute

Pharmacy Phriday #7: Bactrim Adverse Events

Contributor: Cheyenne Bean, PharmD

Educational Pearls:

  • Bactrim (TMP-SMX) is a sulfa antibiotic used for a number of infections but can have untoward effects.
  • Hypoglycemia can be induced by the sulfa component of Bactrim, which binds receptors in the pancreas causing insulin to be secreted, dropping blood sugar levels.
    • Oral diabetic medications, specifically sulfonylureas, when taken with Bactrim most often lead to these hypoglycemic episodes.
  • Hyperkalemia can be induced by Trimethoprim by blocking potassium excretion in the kidney, so Bactrim in combination with ACE inhibitors/ARBs/spironolactone can induce high potassium.
  • When prescribing Bactrim, remember to check home medications and if a patient is taking an above medication, check a baseline BGL and potassium.


1) Khorvash F, Moeinzadeh F, Saffaei A, Hakamifard A. Trimethoprim-sulfamethoxazole Induced Hyponatremia and Hyperkalemia, The Necessity of Electrolyte Follow-up in Every Patient. Iran J Kidney Dis. 2019 Jul;13(4):277-280. PMID: 31422395.

2) Kennedy KE, Teng C, Patek TM, Frei CR. Hypoglycemia Associated with Antibiotics Alone and in Combination with Sulfonylureas and Meglitinides: An Epidemiologic Surveillance Study of the FDA Adverse Event Reporting System (FAERS). Drug Saf. 2020 Apr;43(4):363-369. doi: 10.1007/s40264-019-00901-7. PMID: 31863282; PMCID: PMC7117991.

Summarized by Jackson Roos, MS4 | Edited by Erik Verzemnieks, MD

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