The association trimethoprim-sulfamethoxazole is considered, at standard doses, compatible with breastfeeding.
A usual therapeutic doses, the exclusively breastfed baby can receive up 0.45 mg/kg daily of trimethoprim and 0.68 mg/kg of sulfamethoxazole, doses much lower than those used for treatment in an infant eight weeks.
However, it is certainly best option to use another antibiotic in the mother when attended prematurity, jaundice, illness in the baby or in the neonatal period.
Avoid use of this antibiotic combination in infants with glucose-6-PD deficiency.
Warning of the manufacturer:
Trimethoprim and sulfamethoxazole are excreted through breast milk. The administration of this association should be avoided in the last trimester of pregnancy and in nursing mothers where the mother or child have a special risk of developing hyperbilirubinemia. In addition, administration of this drug combination should be avoided in infants younger than 8 weeks, given the predisposition of these children to suffer hyperbilirubinemia.