What is the best antibiotic for mastitis in a breastfeeding woman?

Best Antibiotic for Mastitis in Breastfeeding Women

For lactational mastitis in breastfeeding women, dicloxacillin 500 mg orally four times daily or cephalexin 500 mg orally four times daily are the first-line antibiotics of choice, as they effectively target methicillin-susceptible Staphylococcus aureus, the most common causative organism. 1

First-Line Antibiotic Selection

• Dicloxacillin 500 mg orally four times daily is the oral agent of choice for methicillin-susceptible S. aureus, which causes the majority of infectious mastitis cases 1
• Cephalexin 500 mg orally four times daily is an equally effective alternative, particularly useful for penicillin-allergic patients 1
• Both cephalosporins and dicloxacillin are considered safe during breastfeeding, with cephalosporins classified as "compatible" with breastfeeding 1, 2
• Dicloxacillin transfers into breast milk at very low levels (maximum concentration 67.6 ng/mL, relative infant dose only 0.03%), well below the 10% threshold of concern 3

Alternative Antibiotics for Specific Situations

For Penicillin-Allergic Patients:

• Erythromycin or azithromycin are acceptable alternatives 1
• Important caveat: There is a very low risk of infantile hypertrophic pyloric stenosis if macrolides are used during the first 13 days of infant life, but they are generally considered safe after this period 1, 2

For Suspected or Confirmed MRSA:

• Consider clindamycin if local MRSA prevalence is high, there is previous MRSA infection, or no response to first-line therapy 1
• Use clindamycin with caution as it may increase GI side effects (particularly diarrhea) in the infant 4, 1, 5
• The FDA label warns that clindamycin can cause antibiotic-associated colitis, which occurs more frequently in elderly patients but can affect infants through breast milk exposure 5

Broad-Spectrum Option:

• Amoxicillin/clavulanic acid is a safe broad-spectrum alternative during breastfeeding based on limited human data 4, 1, 2

Treatment Approach and Monitoring

• Continue breastfeeding during antibiotic treatment - this does not pose a risk to the infant and actually helps resolve the mastitis through regular breast emptying 1, 6
• Reassess within 48-72 hours if symptoms worsen or do not improve, to rule out abscess formation (occurs in approximately 10% of mastitis cases) 1, 6
• Consider obtaining culture results if initial therapy fails, and adjust antibiotics accordingly 1
• Monitor the breastfed infant for gastrointestinal effects such as diarrhea, candidiasis (thrush, diaper rash), or rarely blood in stool 2, 5

Critical Pitfalls to Avoid

• Do not discontinue breastfeeding - continued milk removal is therapeutic and prevents complications 1, 6
• Avoid doxycycline unless absolutely no alternative exists, and if used, limit to 3 weeks maximum without repeating courses 4, 2
• Do not delay antibiotic therapy when indicated - early treatment prevents abscess formation 6
• Ensure adequate hydration when taking dicloxacillin - take with at least 4 fluid ounces (120 mL) of water and NOT in the supine position or immediately before bed, as rare cases of esophageal ulceration have been reported 7

When to Escalate Care

• If an abscess develops despite appropriate antibiotic therapy, surgical drainage or needle aspiration is required 6
• Breastfeeding can usually continue even in the presence of a treated abscess 6