Azithromycin Safety During Breastfeeding
Azithromycin is classified as "probably safe" for use during breastfeeding and can be used when clinically indicated, though it should ideally be avoided during the first 13 days postpartum due to a very low risk of infantile hypertrophic pyloric stenosis (IHPS). 1
Safety Classification and Evidence
The European Respiratory Society/Thoracic Society of Australia and New Zealand (ERS/TSANZ) and the American Academy of Dermatology classify azithromycin as "probably safe" during breastfeeding, representing the second-highest safety designation for antibiotics in lactation. 1
The FDA drug label states that it is not known whether azithromycin is excreted in human milk, and caution should be exercised when administering to nursing women. 2
Azithromycin is specifically recommended as the macrolide of choice for infants younger than 1 month when maternal antibiotic therapy is required, as it has not been linked to IHPS unlike erythromycin. 1
Timing Considerations and Risk Assessment
Avoid azithromycin during the first 13 days postpartum if possible, as there is a very low risk of hypertrophic pyloric stenosis in infants exposed to macrolides during this early period; this risk does not persist after 2 weeks. 1
A pharmacokinetic study in Gambian women found that the median relative cumulative infant dose was 15.7% of the maternal dose (exceeding the recommended 10% safety limit), with a worst-case number needed to harm for IHPS of 60. 3
Parents should be counseled to watch for signs of IHPS—such as projectile vomiting and dehydration—if azithromycin is used during the early postpartum period, though the absolute risk remains very low. 1
Clinical Decision Algorithm
First-line alternatives: Consider amoxicillin/clavulanic acid (classified as "compatible" with breastfeeding, the highest safety designation) as the preferred first-line antibiotic when appropriate for the infection. 1, 4
For penicillin-allergic patients: Azithromycin serves as a good alternative, particularly after the first 2 weeks postpartum. 1
After 2 weeks postpartum: Azithromycin can be used without significant concern for IHPS, as the risk does not persist beyond this period. 1
Infant Monitoring Requirements
All breastfed infants should be monitored for gastrointestinal effects (diarrhea, gastroenteritis) due to alteration of intestinal flora. 1
Antibiotics in breast milk could potentially cause falsely negative cultures if the breastfed infant develops fever requiring evaluation. 1
Common Pitfalls to Avoid
Do not unnecessarily avoid azithromycin after 2 weeks postpartum when it is the most appropriate antibiotic for the maternal infection, as the IHPS risk is limited to the first 13 days. 1
Do not use azithromycin as first-line therapy when safer alternatives like amoxicillin/clavulanic acid (classified as "compatible") are available and appropriate for the infection. 1, 4
Do not discontinue breastfeeding when azithromycin is prescribed, as most antibiotics in clinical use are considered suitable during breastfeeding when the pharmacokinetic profile is appropriate. 5