Nalidixic acid is considered compatible with breastfeeding.
The available information suggests that doses less than or equal to 2000 mg produce a slight rise of the substance in the blood, so that no adverse effects are expected on the baby. An observational study estimated that the amount of drug that an infant could ingest not exceeds 300 mcg per day, under the assumption that doses taken by the mother is equal to or less than 2000 mg/day . Despite the above expressed, for most experts, is considered preferable to use another antibacterial in breastfeeding mothers.
A communication registers a case of hemolysis in a neonate with 16 days of life whose mother received 4000 mg daily of nalidixic acid one week before the onset of the disorder. The baby presented anemia, hyperbilirubinemia, reticulocytosis, eosonofilia and Heinz bodies.
Warning of the manufacturer:
Nalidixic acid is excreted through breast milk, which should be considered when prescribing to a nursing woman.