Is azithromycin (Z-pack) safe during breastfeeding?

Is Z-Pack (Azithromycin) Safe for Breastfeeding?

Yes, azithromycin is considered safe for use during breastfeeding, classified as "probably safe" by major international guidelines, though it carries a very low risk of hypertrophic pyloric stenosis if used within the first 13 days postpartum. 1

Safety Classification

• The European Respiratory Society/Thoracic Society of Australia and New Zealand (ERS/TSANZ) guidelines classify azithromycin as "probably safe" during breastfeeding, which is the second-highest safety designation for antibiotics during lactation. 1

• The American Academy of Dermatology suggests azithromycin as a safe alternative, particularly for penicillin-allergic patients. 1

• The FDA drug label states that "it is not known whether azithromycin is excreted in human milk" and recommends caution, though this conservative stance reflects lack of formal testing rather than evidence of harm. 2

Infant Exposure and Risk Profile

• Research demonstrates that azithromycin transfers into breast milk with a median relative cumulative infant dose of 15.7% of the maternal dose (range 2.0-27.8%), which exceeds the traditional 10% safety threshold used for drug transfer. 3

• There is a very low risk of hypertrophic pyloric stenosis in infants exposed to macrolides during the first 13 days of breastfeeding, but this risk does not persist after 2 weeks. 1 The worst-case number needed to harm is estimated at 60 infants. 3

• Azithromycin demonstrates a time-dependent concentration profile in breast milk rather than accumulation over time. 4

Essential Monitoring Recommendations

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

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

• Watch for changes in stool pattern or consistency in the breastfed infant. 5

Clinical Decision Algorithm

For routine infections:

• Consider amoxicillin/clavulanic acid as first-line if appropriate for the infection, as it is classified as "compatible" (the highest safety designation) rather than "probably safe." 1, 5

For penicillin-allergic patients:

• Azithromycin is an appropriate choice and should not be withheld. 1

For infants under 2 weeks of age:

• Ideally avoid azithromycin during the first 13 days postpartum due to pyloric stenosis risk, but use if clinically necessary as the absolute risk remains very low. 1

For infants over 2 weeks of age:

• Azithromycin can be used without special concern beyond routine monitoring for GI effects. 1

Important Caveats

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

• These safety recommendations assume full-term, healthy infants, standard recommended doses and durations, and exclusive breastfeeding. 1

• Breastfeeding should not be interrupted when azithromycin is prescribed, as the benefits of continued breastfeeding outweigh the minimal risks of azithromycin exposure through breast milk. 1