Last update March 11, 2022


Likely Compatibility

Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.

A short-acting sulfonamide with similar properties to sulfamethoxazole. Rarely administered systemically due to its toxicity (ChemIDplus/ant. Toxnet 2009). Used topically along with other medications for the treatment of vaginal, dermatological, ocular, otic and gastrointestinal infections.

Since the last update we have not found published data on its excretion in breastmilk.

Sulfonamides are excreted in small amounts in breastmilk: 6 to 94 micrograms/ml, 1.6% of the total dose. (Briggs 2017) 

Reports of adverse effects are rare (Briggs 2017). An old publication reports cases of diarrhea and rash in children breastfed by mothers who were being treated with sulfathiazole. (Von Friesen 1951).

Due to the greater toxicity than that of other antimicrobials and their high acquired resistance, the use of sulfonamides is currently very scarce. (Perez 2003)


The small dose and poor plasma absorption of most topical ophthalmological, otic and dermatological preparations make it unlikely that significant amounts will transfer into breastmilk.

Sulfathiazole is absorbed in very small amounts through the dermis (Waud 1944) and the intestine. (Lasca 2018) 

Do not apply to the breast in order to prevent the infant from ingesting it; if necessary, apply after a feed and clean well with water before the next one.


Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

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

N1-(1,3-Thiazol-2-yl)sulphanilamide is Sulfathiazole in Chemical name.

Is written in other languages:

N1-(1,3-Thiazol-2-yl)sulphanilamide is also known as


Main tradenames from several countries containing N1-(1,3-Thiazol-2-yl)sulphanilamide in its composition:


Variable Value Unit
Oral Bioavail. 10 %
Molecular weight 255 daltons
Protein Binding 60 %
pKa 7.2 -
Tmax 3 - 4 hours
4 - 5 hours


  1. Lasca. Sulfatiazol. Ficha técnica. 2018 Full text (in our servers)
  2. Taku-E. Sulfathiazole. Drug Summary. 2018 Full text (in our servers)
  3. Briggs GG, Freeman RK, Towers CV, Forinash AB. Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. Wolters Kluwer Health. Tenth edition (acces on line) 2015
  4. ChemIDplus / ant. Toxnet. Sulfathiazole. None 2009 Full text (link to original source) Full text (in our servers)
  5. Pérez-Trallero E, Iglesias L. Tetraciclinas, sulfamidas y metronidazol. [Tetracyclines, sulfonamides and metronidazole]. Enferm Infecc Microbiol Clin. 2003 Nov;21(9):520-8; quiz 529, 533. Review. Spanish. Abstract Full text (link to original source)
  6. VON FRIESEN B. A study of small dose sulphamerazine prophylaxis in obstetrics, including investigations on the transmission of the drug to foetal blood and urine, amniotic fluid and breast milk. Acta Obstet Gynecol Scand Suppl. 1951;31(3):1-116. (cit Briggs 2015). Abstract
  7. Waud RA. The Absorption of Sulfathiazole from Wounds. Can Med Assoc J. 1944 Abstract Full text (link to original source)
  8. Sadusk JF, Blake FG, Seymour A. Observations on the Absorption, Excretion, Diffusion, and Acetylation of Sulfathiazole in Man. Yale J Biol Med. 1940 Abstract Full text (link to original source)

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