What antibiotics are recommended for a lactating woman with a breast infection?

Recommended Antibiotics for Lactational Breast Infection (Mastitis)

For lactating women with breast infection (mastitis), 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—and are safe during breastfeeding. 1

First-Line Antibiotic Selection

Primary Recommendations

• 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 medications are classified as compatible with breastfeeding, with minimal transfer to breast milk 1, 2

Safety During Breastfeeding

• Penicillins and cephalosporins are excreted in breast milk but are considered safe for nursing infants 3, 2
• Continued breastfeeding during antibiotic treatment is strongly recommended—it does not pose risk to the infant and actually helps resolve the mastitis through regular breast emptying 1
• All breastfed infants should be monitored for mild gastrointestinal effects (diarrhea, candidiasis) due to alteration of intestinal flora 4

Alternative Antibiotics for Special Circumstances

Broad-Spectrum Option

• Amoxicillin/clavulanic acid is a safe broad-spectrum alternative during breastfeeding, classified as FDA Category B and compatible with nursing 1, 4
• This option provides coverage against beta-lactamase-producing bacteria 4

For Penicillin-Allergic Patients

• Erythromycin or azithromycin are acceptable alternatives for penicillin-allergic patients 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; they are generally considered safe after this period 1, 4
• Azithromycin is classified as "probably safe" and should ideally be avoided during the first 13 days postpartum 4

For Suspected or Confirmed MRSA

• Consider MRSA coverage if there is high local MRSA prevalence, previous MRSA infection, or no response to first-line therapy 1
• Clindamycin is an option for MRSA, but use with caution as it may increase GI side effects in the infant, including diarrhea, candidiasis, or rarely antibiotic-associated colitis 1, 5
• The FDA label confirms that clindamycin appears in human breast milk (less than 0.5 to 3.8 mcg/mL) and has potential to cause adverse effects on the infant's gastrointestinal flora 5
• Monitor the breast-fed infant for possible adverse effects such as diarrhea, candidiasis (thrush, diaper rash), or rarely blood in stool indicating antibiotic-associated colitis 5
• Recent evidence suggests MRSA is increasingly common in breast abscesses, particularly in lactating mothers 6

Critical Management Principles

Treatment Duration and Monitoring

• If symptoms worsen or do not improve within 48-72 hours of starting antibiotics, reevaluation is necessary to rule out abscess formation 1
• Breast abscess is the most common complication, occurring in approximately 10% of mastitis cases 1, 7
• Consider alternative antibiotics based on culture results if initial therapy fails 1

Conservative Management First

• For mastitis without fever, starting with frequent breast emptying allows many cases (14-20%) to resolve without antibiotics within 3 months 1
• Add antibiotics if symptoms do not improve within 12-24 hours of conservative management, as delaying treatment risks abscess formation 1

Breastfeeding Continuation

• Do not discontinue breastfeeding—regular breast emptying through continued breastfeeding is essential for resolution 1, 7
• Breastfeeding can usually continue even in the presence of a treated abscess 7

Common Pitfalls to Avoid

• Do not prescribe tetracyclines or fluoroquinolones as first-line treatment during breastfeeding due to potential impacts on infant development 1, 2
• Avoid delaying antibiotic therapy when clinically indicated, as this increases risk of abscess formation (10% of cases) 1
• Do not assume amoxicillin/clavulanic acid alone is adequate for empirical therapy—dicloxacillin or cephalexin provide more targeted S. aureus coverage 1
• Take dicloxacillin with at least 4 fluid ounces (120 mL) of water and NOT in the supine position or immediately before bed to minimize risk of esophageal irritation 3
• Monitor for MRSA risk factors—if present, empirical MRSA coverage may be warranted from the start rather than waiting for treatment failure 1, 6