Safety of Keflex (Cephalexin) During Breastfeeding
Keflex (cephalexin) is considered safe to use during breastfeeding as the amount transferred into breast milk is minimal, with relative infant exposure of only about 0.5% of the maternal dose. 1
Transfer into Breast Milk and Infant Exposure
Cephalexin is excreted in human milk but reaches relatively low concentrations. Studies show the drug reaches a maximum level of 4 mcg/mL in breast milk within 4 hours after a 500 mg dose and disappears completely by 8 hours after administration. 2
The average concentration of cephalexin in breast milk has been measured at approximately 745 microg/L, corresponding to an absolute infant dose of 112 μg/kg/day and a relative infant dose of only 0.5% of the maternal dose. 1
This level of exposure is well below the notional 10% level of concern for infant exposure to medications through breast milk. 1
Potential Side Effects in Breastfed Infants
While systemic effects in the infant are unlikely due to the low relative dose, local gastrointestinal effects such as diarrhea have been reported in some breastfed infants. 1
In one documented case, an infant developed severe diarrhea when the mother was treated with cephalexin and probenecid for a breast infection. The adverse effect was rated as "probable" for cephalexin using the Naranjo probability scale. 1
Mothers should monitor their infants for signs of gastrointestinal disturbance, particularly diarrhea, and contact a healthcare provider if these occur. 1
Recommendations for Use During Breastfeeding
Cephalosporins as a class, including cephalexin, are considered appropriate for use in lactating women. 3
Short courses of antibiotics like cephalexin are commonly used and there is no evidence of harmful effects in breastfeeding women when used appropriately. 4
There is no need to interrupt breastfeeding when taking cephalexin. 3
When prescribing cephalexin to breastfeeding mothers, using dosages at the lower end of the recommended range may help minimize potential infant exposure while maintaining therapeutic effect. 3
Important Considerations
The FDA drug label for cephalexin states: "The excretion of cephalexin in human milk increased up to 4 hours after a 500 mg dose; the drug reached a maximum level of 4 mcg/mL, then decreased gradually, and had disappeared 8 hours after administration. Caution should be exercised when cephalexin is administered to a nursing woman." 2
The benefits of treating maternal infection with appropriate antibiotics generally outweigh the minimal risks to the breastfed infant. 5
If a breastfed infant develops diarrhea while the mother is taking cephalexin, healthcare providers should consider the possibility that it may be related to maternal medication use. 1