Last update Feb. 20, 2016


Very Low Risk

Safe. Compatible. Minimal risk for breastfeeding and infant.

It is excreted in breast milk in clinically non-significant amount. No problems have been observed in infants whose mothers were treated.

Medication which is used in infants from the second month of age.

Take into account the possibility of negative false results of cultures from febrile infants whose mothers are taking antibiotics as well as the possibility of acute diarrhea due to imbalance of the intestinal flora.

The American Academy of Pediatric states that it is usually compatible with breastfeeding medication.
WHO List of Essential Medicines from 2002 has classified it as compatible with breastfeeding.


We do not have alternatives for Trimethoprim since it is relatively safe.

Suggestions made at e-lactancia are done by APILAM team, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

Your contribution is essential for this service to continue to exist. We need the generosity of people like you who believe in the benefits of breastfeeding.

Thank you for helping to protect and promote breastfeeding.

José María Paricio, founder of e-lactancia.

Other names

Trimethoprim is also known as

Trimethoprim in other languages or writings:


Trimethoprim belongs to this group or family:


Main tradenames from several countries containing Trimethoprim in its composition:


Variable Value Unit
Oral Bioavail. 100 %
Molecular weight 290 daltons
Protein Binding 45 %
Tmax 1 - 4 hours
T1/2 8 - 10 hours
M/P ratio 1.3 -
Theoretical Dose 0.3 - 0.8 mg/Kg/d
Relative Dose 6 - 15 %
Ped.Relat.Dose 4 - 10 %


  1. Butler DC, Heller MM, Murase JE. Safety of dermatologic medications in pregnancy and lactation: Part II. Lactation. J Am Acad Dermatol. 2014 Mar;70(3):417.e1-10; quiz 427. Abstract
  2. Mitrano JA, Spooner LM, Belliveau P. Excretion of antimicrobials used to treat methicillin-resistant Staphylococcus aureus infections during lactation: safety in breastfeeding infants. Pharmacotherapy. 2009 Sep;29(9):1103-9. Abstract
  3. Kaiser J, McPherson V, Kaufman L, Huber T. Clinical inquiries. Which UTI therapies are safe and effective during breastfeeding? J Fam Pract. 2007 Abstract
  4. Forna F, McConnell M, Kitabire FN, Homsy J, Brooks JT, Mermin J, Weidle PJ. Systematic review of the safety of trimethoprim-sulfamethoxazole for prophylaxis in HIV-infected pregnant women: implications for resource-limited settings. AIDS Rev. 2006 Abstract
  5. WHO / UNICEF. BREASTFEEDING AND MATERNAL MEDICATION Recommendations for Drugs in the Eleventh WHO Model List of Essential Drugs. Department of Child and Adolescent Health and Development (WHO/UNICEF) 2002 Full text (link to original source) Full text (in our servers)
  6. AAP - American Academy of Pediatrics Committee on Drugs. Transfer of drugs and other chemicals into human milk. Pediatrics. 2001 Sep;108(3):776-89. Abstract Full text (link to original source) Full text (in our servers)
  7. Chin KG, McPherson CE 3rd, Hoffman M, Kuchta A, Mactal-Haaf C. Use of anti-infective agents during lactation: Part 2--Aminoglycosides, macrolides, quinolones, sulfonamides, trimethoprim, tetracyclines, chloramphenicol, clindamycin, and metronidazole. J Hum Lact. 2001 Feb;17(1):54-65. Abstract
  8. Ito S, Blajchman A, Stephenson M, Eliopoulos C, Koren G. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 1993 May;168(5):1393-9. Abstract
  9. Fulton B, Moore LL. Antiinfectives in breastmilk. Part II: Sulfonamides, tetracyclines, macrolides, aminoglycosides and antimalarials. J Hum Lact. 1992 Dec;8(4):221-3. Review. No abstract available. Abstract
  10. Borderon E, Soutoul JH et al. [Excretion of antibiotics in human milk]. Med Mal Infect. 1975;5:373-6. 1975
  11. Miller RD, Salter AJ. \ The passage of trimethoprim/sulpha-methoxazole into breast milk and its significance. \ Proceedings of the 8th International Congress of Chemotherapy, Athens. Hellenic Soc Chemother. 1974;1:687. 1974
  12. Arnauld R, Soutoul JH, Gallier J et al. Etude du passage de la trimethprim dans le lait maternel. \ [Study on the passage of trimethoprin into mother's milk]. Ouest Med. 1972;25:959-64.4. 1972
  13. Rasmussen F. \ Mammary excretion of sulphonamides. Acta Pharmacol Toxicol 1958; 15: 139-48. 1958

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