Keflex (Cephalexin) is Safe During Breastfeeding for Mastitis Treatment
Mothers with mastitis should continue breastfeeding while taking Keflex (cephalexin), as cephalosporins are considered compatible with breastfeeding and only minimal amounts transfer into breast milk, posing negligible risk to the infant. 1, 2
Effect on Breast Milk
Cephalexin excretion into breast milk is minimal and time-limited. The drug reaches a maximum level of 4 mcg/mL at 4 hours after a 500 mg dose, then decreases gradually and disappears by 8 hours after administration 2
Oral absorption by the infant is minimal because cephalosporins have low oral bioavailability, meaning even the small amount in breast milk is poorly absorbed by the baby's gastrointestinal tract 1
Cephalosporins, including cephalexin, are classified as compatible with breastfeeding according to major guidelines 1
Effect on the Baby
No clinically significant adverse effects are expected in breastfed infants when mothers take cephalexin at standard doses 1, 3
The most common potential effect is mild alteration of intestinal flora, which could theoretically cause mild diarrhea, though this is rare 1
Systemic antibiotics in breast milk could potentially cause falsely negative cultures if the infant becomes febrile and requires evaluation, though this is a theoretical concern rather than a contraindication 1
Infants should be monitored for uncharacteristic symptoms, but serious toxicity is not expected with cephalosporins 4
Clinical Management Algorithm
First-Line Approach for Mastitis
Continue breastfeeding or milk expression during mastitis treatment - this is essential for resolution and prevents complications 5, 6
Cephalexin (Keflex) is a preferred antibiotic choice for mastitis as it effectively targets Staphylococcus aureus, the most common causative organism 6
Standard dosing should be maintained without modification for breastfeeding 2
Timing Considerations
No need to "pump and dump" or avoid breastfeeding at specific times after taking cephalexin 1
If mothers wish to minimize infant exposure (though not medically necessary), they could theoretically breastfeed immediately before taking the medication, as peak milk levels occur 1-4 hours post-dose 2, 4
Important Caveats
Continued breastfeeding is crucial for mastitis resolution - approximately 10% of mastitis cases progress to breast abscess if not properly treated, and regular milk removal is a key component of therapy 5, 6
Breastfeeding should continue even on the affected breast, as long as the infant's mouth does not contact purulent drainage if an abscess has developed 5
The benefits of continued breastfeeding far outweigh the minimal theoretical risks of cephalexin exposure through breast milk 1, 3
Premature cessation of breastfeeding due to unnecessary concerns about antibiotics causes more harm than the negligible drug exposure, including risks of breast engorgement, blocked ducts, formula intolerance, and loss of breastfeeding's protective benefits 5, 7