Is Trimethoprim-Sulfamethoxazole safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Trimethoprim-Sulfamethoxazole. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
An extensive systematic review of the use of sulfonamides near term and during breastfeeding found no adverse reactions in infants. The authors concluded that use of sulfamethoxazole-trimethoprim during breastfeeding presents no risk of neonatal kernicterus.[ 7 ] A prospective, controlled study asked mothers who called an information service about adverse reactions experience by their breastfed infants. Of 12 women who took sulfamethoxazole and trimethoprim during breastfeeding (time postpartum and dosage not stated), none reported diarrhea, drowsiness or irritability in her infant. Two mothers reported poor feeding in their infants.[ 8 ]
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
Maternal Levels. In 20 mothers in the immediate postpartum period given oral trimethoprim, peak milk levels occurred 3 hours after the dose. In 14 of these women who received a daily dosage of 320 mg, the peak milk level averaged 2.4 mg/L and the trough averaged 1 mg/L. In 6 other women who received a daily dosage of 480 mg, the peak milk level averaged 4 mg/L and the trough averaged 1.5 mg/L. The authors calculated that a breastfed infant would receive a daily dosage of 0.75 mg with a maternal dosage of 320 mg daily and 1.7 mg with a maternal dosage of 480 mg.[ 4 , 5 ] Forty women who were 5 or fewer days postpartum period received oral co-trimoxazole equivalent to 800 mg of sulfamethoxazole and 320 mg of trimethoprim twice daily. Another 10 women were given this dose 3 times daily. Milk levels were measured several times daily for 5 days. After trimethoprim doses of 320 mg daily, average milk levels were about 2 mg/L in both groups. Milk levels increased to about 3 mg/L by day 5 of therapy. Average sulfamethoxazole milk levels were 4.5 and 5.3 mg/L, respectively, with the 2 doses.[ 6 ] With the usual dose of trimethoprim 320 mg and sulfamethoxazole 800 mg daily, an exclusively breastfed infant would be expected to receive 0.45 mg/kg daily of trimethoprim and 0.68 mg/kg daily of sulfamethoxazole. This is very low in comparison to the established treatment dosages of 8 mg/kg and 40 mg/kg daily for infants over 2 months of age. Infant Levels. Relevant published information was not found as of the revision date.
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.