Gentamicin is poorly excreted into breastmilk. Newborn infants apparently absorb small amounts of gentamicin, but their serum levels with three times daily dosages are far below those attained when treating newborn infections and systemic effects of gentamicin are unlikely. Older infants would be expected to absorb even less gentamicin. Because there is little variability in the milk gentamicin levels during multiple daily dose regimens, timing breastfeeding with respect to the dose is of little or no benefit in reducing infant exposure. Data are not available with single daily dose regimens. Monitor the infant for possible effects on the gastrointestinal flora, such as diarrhea, candidiasis (e.g., thrush, diaper rash) or rarely, blood in the stool indicating possible antibiotic-associated colitis.
Maternal use of an ear drop or eye drop that contains gentamicin presents little or no risk for the nursing infant.[1]