What antibiotics are recommended for treating mastitis?

Antibiotics for Mastitis

For lactational mastitis in breastfeeding women, first-line antibiotic therapy should be dicloxacillin or cephalexin (e.g., cephalexin 500 mg four times daily), both of which are safe during breastfeeding and effectively target Staphylococcus aureus, the most common causative organism. 1, 2

First-Line Antibiotic Selection

Preferred agents:

• 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 3, 2
• Cephalexin 500 mg orally four times daily is an equally effective alternative, particularly for penicillin-allergic patients (except those with immediate hypersensitivity reactions) 3, 1

Both antibiotics demonstrate minimal transfer into breast milk and are considered compatible with continued breastfeeding. Dicloxacillin has a relative infant dose of only 0.03%, well below the 10% threshold of concern 4.

Alternative Antibiotics for Special Circumstances

For penicillin-allergic patients:

• Erythromycin or azithromycin are appropriate alternatives 1
• Caution: Monitor infants for gastrointestinal side effects and be aware of a very low risk of hypertrophic pyloric stenosis if macrolides are used during the first 13 days of breastfeeding 5, 1

For suspected or confirmed MRSA:

• Consider MRSA coverage if local prevalence is high, patient has previous MRSA infection, or no response to first-line therapy within 48-72 hours 1
• Options include clindamycin, though use with caution as it may increase GI side effects in the infant 3, 5

Broad-spectrum option:

• Amoxicillin/clavulanic acid is safe during breastfeeding and provides broader coverage 5, 1

Critical Management Principles

Continue breastfeeding:

• Continued breastfeeding during antibiotic treatment does not pose risk to the infant and actually helps resolve the mastitis through regular breast emptying 1, 2
• This is essential for both treatment success and prevention of abscess formation 2

Reassessment timeline:

• If symptoms worsen or fail to improve within 48-72 hours of starting antibiotics, reevaluate to rule out breast abscess (occurs in approximately 10% of mastitis cases) 1, 2
• Consider culture-directed therapy if initial treatment fails 1

Common Pitfalls to Avoid

• Do not discontinue breastfeeding - this worsens the condition and increases abscess risk 2
• Avoid tetracyclines (including doxycycline) and fluoroquinolonas due to potential impacts on infant development 1
• Do not delay antibiotic therapy in symptomatic patients - early treatment prevents complications and faster symptom resolution 2, 6
• Optimize breastfeeding technique concurrently with antibiotics, ideally with lactation consultant assistance, as poor positioning contributes to mastitis development 2