Flagyl (metronidazole) is a drug used to treat systemic, intestinal, and vaginal infections. Flagyl has been shown to concentrate in breast milk but there hasn’t been any documented adverse effects in breastfed babies. However, there have been reports of babies becoming “fussy” once a mother is started on a course of Flagyl. Some pediatricians believe that breastfeeding can be done safely on metronidazole others err on the side of caution and recommend formula feeds until the mother is off Flagyl. I favor the latter and recommend my patients to formula feeds until 24 hours after their last dose of Flagyl.