Nitrofurantoin Use During Lactation
Nitrofurantoin is generally compatible with breastfeeding and can be safely used in lactating women, though caution is warranted for infants under 1 month of age or those with glucose-6-phosphate dehydrogenase (G6PD) deficiency. 1, 2
Safety Profile in Lactation
Nitrofurantoin is actively transported into breast milk, achieving milk concentrations 6 times higher than serum levels (milk:serum ratio of 6.21), which is substantially greater than the predicted ratio of 0.28. 2
Despite this active transport, the absolute amount transferred to the infant remains low: only 0.05-0.29% of the maternal dose is excreted into milk within 6 hours of administration. 3
The estimated infant exposure is approximately 0.2 mg/kg/day, representing only 6% of the weight-adjusted maternal dose. 2
Average milk concentrations reach 1.3 mg/L, which is well below therapeutic levels and unlikely to cause systemic effects in most infants. 2
Clinical Recommendations
For pregnant women with asymptomatic bacteriuria requiring treatment, nitrofurantoin should be given for 4-7 days rather than single-dose therapy, as longer courses are more effective at preventing adverse outcomes including low birth weight. 1
- Nitrofurantoin is preferred for treating uncomplicated urinary tract infections during both pregnancy and lactation due to its established safety record spanning over 35 years and lack of resistance development. 4
Critical Contraindications and Precautions
Avoid nitrofurantoin in breastfeeding mothers whose infants are:
- Less than 1 month of age (risk of hemolytic anemia due to immature enzyme systems) 2, 5
- Known or suspected G6PD deficiency (risk of hemolytic crisis) 2
- Showing signs of nitrofurantoin sensitivity 2
Practical Prescribing Guidance
For full-term, healthy infants beyond 1 month of age being exclusively breastfed, nitrofurantoin poses minimal risk and breastfeeding should be encouraged. 1
The relative infant dose of 6% is well below the 10% threshold generally considered safe for lactation. 1, 2
No specific timing of breastfeeding relative to dosing is necessary, as the drug is rapidly cleared (half-life 0.8 hours) and infant exposure remains consistently low. 3
Monitor neonates for signs of hemolysis (jaundice, pallor, dark urine) if treatment extends beyond a few days, particularly in populations with higher G6PD deficiency prevalence. 2