Last update Jan. 29, 2022


Likely Compatibility

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

Sulphamide similar to sulfamethoxazole. It is used together with other antibacterials in the treatment of intestinal infections and in intestinal decontamination prior to surgery.

Since the last update we have not found published data on its excretion in breastmilk. Its very low oral bioavailability minimizes both the excretion in breast milk and the passage into plasma of the infant from ingested breast milk

It remains in the intestine without being absorbed; only 5% does so in the form of sulfathiazole (Martindale, acc.2022). Its very low oral bioavailability minimizes both excretion in breast milk and passage to infant plasma from ingested breast milk.

Sulphamides are excreted in small amounts in breast milk: 6 to 94 micrograms/ml, 1.6% of the total dose. (Briggs 2015)

Reports of adverse effects are rare (Briggs 2015). Avoid in suspected glucose-6-phosphate dehydrogenase deficiency.  

Due to the greater toxicity than other antimicrobials and their high acquired resistance, the use of sulfonamides is currently very scarce (Pérez 2003). Product with very few bibliographic and/or very old references, marketed in few countries.

See below the information of this related product:

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


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

Phthalylsulfathiazole is also known as

Phthalylsulfathiazole in other languages or writings:


Main tradenames from several countries containing Phthalylsulfathiazole in its composition:


Variable Value Unit
Oral Bioavail. 5 %
Molecular weight 403 daltons
pKa 2.91 -


  1. Royal Pharmaceutical Society. Martindale: The Complete Drug Reference Medicines Complete. available online from: 2022 Abstract
  2. 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
  3. 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)

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