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This monograph summarizes lactation‑related toxicology for medicines classified in ATC subgroup A07AA01 (neomycin as intestinal antibiotic), focusing on maternal use during breastfeeding and potential effects in breastfed infants.atcddd.fhi+2

Active substance and ATC classification

A07AA01 designates neomycin, an aminoglycoside antibiotic classified under intestinal antiinfectives and used orally in the treatment of intestinal infections or for bowel decontamination.atcddd.fhi+2
Neomycin is also assigned multiple other ATC codes for systemic, topical, ophthalmic, otic and oral–pharyngeal preparations, but this monograph focuses on its use as A07AA01 oral intestinal antibiotic.drugbank+1

Pharmacology and indications

Neomycin is a broad‑spectrum aminoglycoside that exerts bactericidal activity by binding to the 30S ribosomal subunit and inhibiting bacterial protein synthesis.drugbank+1
Oral neomycin is used as an adjunct in intestinal infections, for reduction of ammonia‑producing gut flora in hepatic encephalopathy, and for preoperative bowel decontamination before colorectal surgery.mayoclinic+1

Pharmacokinetics relevant to lactation

After oral administration, neomycin is poorly absorbed from the intact gastrointestinal tract, with most of the dose remaining within the gut lumen and being excreted unchanged in feces.drugbank+1
Systemic absorption may increase in the presence of mucosal damage, high doses, prolonged therapy, or in neonates and premature infants, raising the potential for measurable serum levels and, theoretically, increased passage into breast milk.pubmed.ncbi.nlm.nih+1

Transfer into breast milk

Direct data on neomycin levels in human milk are limited, but by analogy with other aminoglycosides, excretion into breast milk appears to be very low when maternal exposure is oral, topical, ophthalmic or otic.drugs+1
Authoritative lactation resources consider neomycin compatible with breastfeeding, stating that oral or topical use results in very low milk levels and negligible risk for the infant under usual therapeutic conditions.drugs+1

Infant systemic exposure and oral absorption

Newborn infants can absorb small amounts of aminoglycosides orally, but reported serum levels after exposure via breast milk are far below those achieved during direct therapeutic dosing in neonates.drugs+1
Older, healthy breastfed infants are expected to absorb even smaller quantities from ingested milk, making clinically relevant systemic toxicity from maternal neomycin exposure unlikely.drugs+1

Potential adverse effects in breastfed infants

The main potential effects in the breastfed infant relate to changes in gastrointestinal flora, manifesting as diarrhea, soft stools, or candidiasis such as oral thrush or diaper rash.drugs+1
Very rarely, antibiotic‑associated colitis with blood in the stool is possible, so caregivers should be advised to seek medical review if the infant develops persistent diarrhea, bloody stools, or significant feeding changes while the mother is on neomycin.drugs

Maternal toxicity considerations impacting lactation

Systemically absorbed neomycin, particularly at high doses or with impaired renal function, carries risks of nephrotoxicity and ototoxicity in adults, although these are uncommon with standard short‑course oral intestinal use.mayoclinic+1
Clinicians should monitor maternal renal function and overall clinical status in high‑risk women, as severe maternal toxicity could indirectly compromise breastfeeding through illness or treatment interruption rather than direct milk‑mediated infant toxicity.mayoclinic+1

Use during breastfeeding: risk assessment

Most contemporary antibiotic safety reviews emphasize that the majority of antibiotics, including many aminoglycosides when used appropriately, can be compatible with breastfeeding, especially when the drug is also acceptable for direct infant therapy.vinmec+1
Given neomycin’s poor oral bioavailability, low expected breast‑milk transfer, and limited infant oral absorption at the doses used in mothers, oral intestinal neomycin (A07AA01) is generally considered very low risk in breastfeeding, provided that dosing remains within standard therapeutic ranges.drugs+1

Higher‑risk situations and precautions

Caution is warranted when breastfeeding premature infants, neonates in the first weeks of life, or infants with gastrointestinal disease, renal impairment, or severe comorbidity, as they may be more susceptible to microbiota disruption or potential systemic accumulation.pubmed.ncbi.nlm.nih+2
In such cases, prescribers should individualize therapy, consider alternative antibiotics if available, and ensure closer monitoring of both maternal condition and infant clinical status.mayoclinic+2

Practical recommendations and monitoring

When neomycin A07AA01 is clinically indicated in a breastfeeding woman, it can usually be prescribed without interrupting lactation, using the lowest effective dose and shortest feasible course.mayoclinic+2
Caregivers should be instructed to observe the breastfed infant for gastrointestinal symptoms, candidiasis or unusual behavior, and to avoid applying neomycin ointments directly to the nipple, with preference for water‑miscible creams or gels on the breast if local treatment is necessary.drugs+1

Evidence gaps and research needs