Use of systemic tetracyclines in women who are lactating.

They write that systemic tetracyclines are contraindicated in women who are nursing. Tetracycline is excreted into breast milk in low concentrations. It binds to calcium in breast milk and is absorbed poorly by the infant. A study of lactating women who were taking 500 mg of tetracycline four times a day found that levels of tetracycline in the infants were below the level of detection (0.05 μg per mL).2,3 Theoretic concerns about the possibility of dental staining or delayed bone growth in the infants seems unlikely at these serum concentrations.3