Is azithromycin (macrolide antibiotic) safe for use in a breastfeeding woman?

Azithromycin Use During Breastfeeding

Yes, azithromycin can be given to a breastfeeding woman and is classified as "probably safe" according to current international guidelines, though there is a very low risk of hypertrophic pyloric stenosis if the infant is exposed during the first 13 days of life. 1, 2

Safety Classification and Recommendations

• The European Respiratory Society/Thoracic Society of Australia and New Zealand (ERS/TSANZ) guidelines classify azithromycin as "probably safe" during breastfeeding (FDA Category B1), making it an acceptable choice when antibiotic therapy is indicated. 1, 2

• The American Academy of Dermatology recommends azithromycin as a safe alternative antibiotic during breastfeeding, particularly for penicillin-allergic patients. 2

• The FDA drug label states that "it is not known whether azithromycin is excreted in human milk" and recommends caution when administering to nursing women, though this conservative language is standard for most medications. 3

Critical Timing Consideration: The First Two Weeks

The most important caveat is timing relative to the infant's age:

• There is a very low risk of hypertrophic pyloric stenosis in infants exposed to macrolides (including azithromycin) during the first 13 days of breastfeeding. 1, 2

• This risk does NOT persist after 2 weeks of age, making azithromycin safer for use when the infant is older than 2 weeks. 1, 2

• If azithromycin must be used during the first 13 days postpartum, the worst-case number needed to harm for pyloric stenosis is approximately 60 based on epidemiological data. 4

Infant Drug Exposure

• Research demonstrates that the median cumulative infant dose through breast milk is approximately 4.5 mg/kg (or 15.7% of the maternal dose), which exceeds the generally recommended 10% safety threshold. 4

• Azithromycin demonstrates a time-dependent accumulation profile in breast milk rather than immediate peak concentrations. 5

• Like all systemic antibiotics, azithromycin will be present in breast milk and could potentially alter the infant's intestinal flora. 1

Required Infant Monitoring

All breastfed infants whose mothers receive azithromycin should be monitored for:

• Gastrointestinal effects including diarrhea or gastroenteritis due to alteration of intestinal flora. 1, 2

• Signs of pyloric stenosis (particularly if exposure occurs in the first 13 days): projectile vomiting, visible peristaltic waves, palpable "olive" mass in the epigastrium. 1, 2

• The presence of antibiotics in breast milk could cause falsely negative bacterial cultures if the infant develops fever requiring sepsis evaluation. 1, 2

Clinical Decision Algorithm

When prescribing azithromycin to a breastfeeding woman:

1. If the infant is >2 weeks old: Azithromycin is "probably safe" - prescribe with standard monitoring for GI effects. 1, 2

2. If the infant is <13 days old: Consider alternative antibiotics first (amoxicillin or cephalosporins are "compatible"), but if azithromycin is clinically necessary, counsel parents about the very low pyloric stenosis risk and ensure close monitoring. 1, 2

3. For penicillin-allergic patients: Azithromycin or erythromycin are appropriate macrolide choices regardless of infant age, with the same timing considerations. 2

Preferred Alternatives (If Applicable)

• Amoxicillin and cephalosporins (including ceftriaxone) are classified as "compatible" with breastfeeding, representing safer first-line options when clinically appropriate. 1, 2

• Amoxicillin/clavulanic acid is explicitly recommended as a safe and effective choice during breastfeeding by multiple guidelines. 2, 6