Is Bactrim (trimethoprim/sulfamethoxazole) safe to use during breastfeeding?

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Last updated: June 9, 2025View editorial policy

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From the Guidelines

Bactrim (trimethoprim/sulfamethoxazole) should be used with caution during breastfeeding, particularly in infants who are glucose-6-phosphate dehydrogenase deficient, jaundiced, or premature, as it can cause hyperbilirubinemia and hemolytic anemia 1.

Key Considerations

  • The medication can pass into breast milk, posing potential risks to the nursing infant, including interference with bilirubin metabolism and an increased risk of jaundice.
  • There is a theoretical risk of hemolytic anemia in infants with G6PD deficiency.
  • Alternative antibiotics, such as penicillins or cephalosporins, are considered safer during lactation and should be considered when appropriate for the infection being treated.

Recommendations

  • Healthcare providers should monitor the infant for signs of jaundice, unusual pallor, or digestive disturbances if the mother is taking Bactrim.
  • The timing of breastfeeding in relation to medication doses can be adjusted to minimize infant exposure, although this strategy has limited effectiveness due to the drug's relatively long half-life in the body.
  • According to the European Respiratory Journal study, Co-trimoxazole (sulfamethoxazole + trimethoprim) is compatible with breastfeeding in healthy term babies, but should be avoided in babies who are glucose-6-phosphate dehydrogenase deficient, jaundiced, or premature 1.

Important Notes

  • The study suggests that most systemic antibiotics will be present in breast milk, which could cause falsely negative cultures in febrile infants or produce gastroenteritis due to alteration of intestinal flora 1.
  • The risk of hypertrophic pyloric stenosis in infants exposed to macrolides during the first 13 days of breastfeeding is very low, but this is not directly related to Bactrim use 1.

From the FDA Drug Label

Levels of sulfamethoxazole and trimethoprim in breast milk are approximately 2% to 5% of the recommended daily dose for infants over 2 months of age Caution should be exercised when sulfamethoxazole and trimethoprim is administered to a nursing woman, especially when breastfeeding jaundiced, ill, stressed, or premature infants because of the potential risk of bilirubin displacement and kernicterus

Bactrim use during breastfeeding is approached with caution, especially in jaundiced, ill, stressed, or premature infants due to the potential risk of bilirubin displacement and kernicterus. The drug is excreted in breast milk at levels of approximately 2% to 5% of the recommended daily dose for infants over 2 months of age 2.

From the Research

Bactrim Use During Breastfeeding

  • Bactrim, also known as trimethoprim/sulfamethoxazole, is an antibiotic used to treat various bacterial infections.
  • The safety of using Bactrim during breastfeeding has been studied, and the results suggest that most antibiotics, including Bactrim, are considered suitable for use during breastfeeding 3, 4.
  • However, it is essential to consider the pharmacokinetic profile of each drug to ensure the resolution of the maternal infection and the safety of the infant 3.
  • Studies have shown that the use of most antibiotics, including sulfonamides and trimethoprim-sulfamethoxazole, is considered compatible with breastfeeding 4, 5.
  • The exposure of the breastfed infant to antibiotics, including Bactrim, has been calculated and expressed as a percentage of a normal infant therapeutic dose, and the results suggest that breastfed infants are exposed to a subtherapeutic concentration of antibiotics 6.

Antibiotic Resistance and Bactrim

  • The resistance rates of Bactrim (trimethoprim-sulfamethoxazole) in the treatment of uncomplicated urinary tract infections have been studied, and the results suggest that resistance to Bactrim is common, especially among Escherichia coli species 7.
  • The study suggests that Bactrim should be excluded from empirical treatment, while fosfomycin could be a viable option in all age groups 7.
  • It is crucial to consider the antibiotic resistance rates when prescribing antibiotics, including Bactrim, during breastfeeding 7.

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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