Nitrofurantoin (Macrobid) Safety During Breastfeeding
Nitrofurantoin is generally safe for breastfeeding mothers, but should be avoided or used with caution in mothers nursing infants under 1 month of age due to theoretical risk of hemolytic anemia, particularly in infants with G6PD deficiency. 1
Key Safety Data
Minimal Drug Transfer into Breast Milk:
- Only 0.05-0.28% of the maternal nitrofurantoin dose is excreted into breast milk within 6 hours of administration 2
- Peak milk concentrations occur at 3 hours post-dose, with milk-to-plasma ratios of approximately 2.2-2.3 2
- The absolute amount transferred is extremely small (22-284 micrograms over 6 hours depending on maternal dose) 2
Age-Specific Recommendations
For Infants Under 1 Month:
- Preferred alternatives include amoxicillin, amoxicillin/clavulanic acid, cephalexin, or ceftriaxone 3, 4
- If nitrofurantoin must be used when no alternative is available, it is not a reason to discontinue breastfeeding, but close monitoring is essential 1
- The theoretical concern stems from newborn glutathione instability, though this may stabilize by day 8 of life 1
For Infants Over 1 Month:
- Nitrofurantoin can be used with standard monitoring 1
- The risk of hemolytic anemia decreases significantly as glutathione systems mature 1
Essential Monitoring Parameters
Watch for these specific signs in the breastfed infant:
- Changes in stool pattern or color 3
- Unusual irritability or lethargy 3
- Poor feeding or decreased appetite 3
- Signs of anemia (pallor, fatigue) if G6PD deficiency is suspected 1
- Gastrointestinal effects from altered intestinal flora 4
Clinical Decision-Making
The benefits of treating maternal UTI outweigh theoretical risks of minimal drug exposure through breast milk 3. Untreated maternal infection poses significant direct risks that must be prioritized 3. However, when treating mothers of very young infants (under 1 month), the safer beta-lactam alternatives should be selected first-line 3, 4.
Important Caveat
If the infant develops fever requiring evaluation while the mother is taking any antibiotic (including nitrofurantoin), be aware that antibiotics in breast milk could cause falsely negative cultures 4.