What antibiotics are safe for a lactating woman with a bacterial infection to use while breastfeeding?

Safe Antibiotics for Breastfeeding

Penicillins (amoxicillin, amoxicillin-clavulanate) and first-generation cephalosporins (cephalexin) are the safest first-line antibiotics for breastfeeding mothers and should be your default choices for most bacterial infections. 1

First-Line Safe Antibiotics

β-lactam antibiotics are the gold standard for breastfeeding mothers:

• Amoxicillin is classified as "compatible" with breastfeeding by the European Respiratory Society and American Academy of Dermatology, representing the highest safety designation for lactation. 1 The FDA classifies it as Pregnancy Category B, and penicillins are excreted in human milk at low concentrations with minimal infant exposure. 1, 2

• Amoxicillin-clavulanate (Augmentin) is explicitly recommended as safe and effective during breastfeeding with FDA Category B classification and "compatible" designation. 1, 3 One important caveat: avoid this combination in women at risk of pre-term delivery due to necrotizing enterocolitis risk, but for postpartum breastfeeding after term delivery, it remains fully safe. 1

• Cephalexin and other first-generation cephalosporins are "compatible" with breastfeeding and particularly recommended for skin and soft tissue infections. 1, 3 Cephalosporins have minimal transfer to breast milk and limited impact on nursing infants. 1

Safe Alternative Antibiotics

For penicillin-allergic patients or specific infections:

• Azithromycin is classified as "probably safe" by the European Respiratory Society, but ideally avoid during the first 13 days postpartum due to a very low risk of hypertrophic pyloric stenosis in exposed infants—this risk does not persist after 2 weeks. 1, 3

• Erythromycin is suggested as safe for penicillin-allergic patients, with the same 13-day postpartum caveat as azithromycin. 1, 3

• Metronidazole is suggested as safe during breastfeeding by the American Academy of Dermatology. 1, 3

• Ceftriaxone and other third-generation cephalosporins are classified as "compatible" with breastfeeding. 3

Antibiotics Requiring Caution

Use these only when specifically indicated, with close infant monitoring:

• Clindamycin should be used with caution as it may increase GI side effects in the infant, including diarrhea, candidiasis, or rarely antibiotic-associated colitis. 1, 3, 4 The FDA drug label confirms clindamycin appears in breast milk at concentrations of less than 0.5 to 3.8 mcg/mL and states that while it's not a reason to discontinue breastfeeding, an alternate drug may be preferred. 4 If clindamycin is specifically indicated, consider topical formulations which have significantly lower systemic absorption. 1

• Doxycycline and tetracyclines should be limited to 3 weeks maximum without repeating courses, and only if no suitable alternative is available. 1, 3 Short-term use (3-4 weeks) is compatible with breastfeeding, but avoid longer courses due to potential tooth discoloration and bone growth suppression. 1

• Co-trimoxazole should be avoided in premature infants, jaundiced babies, or those with G6PD deficiency. 3

Antibiotics to Avoid as First-Line

Reserve these for specific indications only:

• Fluoroquinolones (ciprofloxacin, levofloxacin) should not be used as first-line treatment during breastfeeding. 1 If absolutely necessary, ciprofloxacin is the preferred fluoroquinolone due to its lower concentration in breast milk—two orders of magnitude lower than therapeutic infant doses. 1

• Aminoglycosides should not be used during breastfeeding due to potential risks to the infant. 1

Essential Infant Monitoring

All breastfed infants whose mothers are taking antibiotics require monitoring:

• Monitor for gastrointestinal effects (diarrhea, gastroenteritis) due to alteration of intestinal flora, though serious adverse events are rare. 1, 3

• Be aware that antibiotics in breast milk could cause falsely negative cultures if the infant develops fever requiring evaluation. 1, 3

• The small amounts of antibiotic in breast milk should not be considered therapeutic for the infant—if the baby develops an infection, they require their own appropriate dosing. 1

Clinical Decision Algorithm

1. Start with amoxicillin or cephalexin for most bacterial infections requiring antibiotic therapy. 1
2. Use amoxicillin-clavulanate for broader spectrum coverage when indicated. 1, 3
3. For penicillin allergy, use azithromycin or erythromycin (avoid first 13 days postpartum if possible). 1, 3
4. For MRSA coverage, consider clindamycin with caution and close infant GI monitoring. 1, 3
5. Continued breastfeeding during antibiotic treatment is recommended and does not pose significant risks to the infant. 1

Key Resource

The NIH LactMed database is a valuable resource for checking specific antibiotic safety during lactation when encountering less common antibiotics. 1