What are the absolute contraindications to Trimethoprim-Sulfamethoxazole (Bactrim)?

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From the Guidelines

Bactrim (trimethoprim-sulfamethoxazole) should never be used in patients with known hypersensitivity to trimethoprim or sulfonamides, history of drug-induced immune thrombocytopenia, patients with documented megaloblastic anemia caused by folate deficiency, pregnant patients and nursing mothers, pediatric patients < 2 months of age, and patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored. The contraindications for Bactrim are clearly outlined in the guidelines of care for the management of acne vulgaris 1. Some key points to consider when prescribing Bactrim include:

  • Known hypersensitivity to trimethoprim or sulfonamides is an absolute contraindication due to the risk of severe allergic reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis 1.
  • Patients with a history of drug-induced immune thrombocytopenia should avoid Bactrim due to the risk of thrombocytopenia and other blood dyscrasias 1.
  • Bactrim is contraindicated in patients with documented megaloblastic anemia caused by folate deficiency, as it can exacerbate this condition 1.
  • Pregnant patients and nursing mothers should not use Bactrim, as it may cause kernicterus in neonates and is distributed into breast milk 1.
  • Pediatric patients < 2 months of age should not be given Bactrim, as its safety and efficacy have not been established in this age group 1.
  • Patients with marked hepatic damage or severe renal insufficiency should avoid Bactrim, as it can cause further renal damage and hepatic necrosis 1.

From the FDA Drug Label

Sulfamethoxazole and trimethoprim tablets USP is contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides, in patients with a history of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides, and in patients with documented megaloblastic anemia due to folate deficiency Sulfamethoxazole and trimethoprim tablets USP is also contraindicated in pregnant patients and nursing mothers, because sulfonamides pass the placenta and are excreted in the milk and may cause kernicterus. Sulfamethoxazole and trimethoprim tablets USP is contraindicated in pediatric patients less than 2 months of age Sulfamethoxazole and trimethoprim tablets USP is also contraindicated in patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored.

The absolute contraindications to Bactrim are:

  • Known hypersensitivity to trimethoprim or sulfonamides
  • History of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides
  • Documented megaloblastic anemia due to folate deficiency
  • Pregnant patients
  • Nursing mothers
  • Pediatric patients less than 2 months of age
  • Marked hepatic damage
  • Severe renal insufficiency when renal function status cannot be monitored
  • Concomitant administration with dofetilide 2 3

From the Research

Absolute Contraindications to Bactrim

  • A known history of hypersensitivity reactions to sulfonamides, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms 4, 5
  • Patients with a history of immediate IgE-mediated reactions to sulfonamides, as cross-reactivity between sulfonamide antimicrobials and sulfonamide non-antimicrobials is unlikely, but the risk of a severe reaction still exists 4
  • Patients with severe cutaneous adverse reactions to sulfonamides, such as photosensitivity, as these reactions can be life-threatening 5

Special Considerations

  • Patients infected with the human immunodeficiency virus (HIV) may experience frequent side effects when taking Bactrim, and alternative treatments should be considered 6
  • Patients with a history of reactions to non-β-lactam antibiotics, including sulfonamides, should be carefully evaluated before starting Bactrim therapy 5

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Sulfonamide Hypersensitivity: Fact and Fiction.

The journal of allergy and clinical immunology. In practice, 2019

Research

Hypersensitivity to non-β-lactam antibiotics.

Allergologie select, 2022

Research

Trimethoprim-sulfamethoxazole.

Mayo Clinic proceedings, 1999

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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