Can amoxicillin (amoxicillin) be used to treat mastitis?

Amoxicillin for Lactational Mastitis Treatment

Amoxicillin can be used to treat lactational mastitis, though the evidence supporting antibiotic therapy for this condition is surprisingly limited, and amoxicillin alone may not be the optimal first-line choice given the predominance of Staphylococcus aureus as the causative organism.

Evidence Quality and Limitations

The evidence base for antibiotic treatment of lactational mastitis is notably weak:

• A Cochrane systematic review found insufficient evidence to confirm or refute the effectiveness of antibiotic therapy for lactational mastitis, identifying only two small trials meeting inclusion criteria 1
• One trial (n=25) directly compared amoxicillin 500 mg orally every 8 hours for 7 days versus cephradine 500 mg orally every 6 hours for 7 days, finding no significant difference in symptom relief or abscess formation between the two antibiotics 1, 2
• Both treatment failures and one of three recurrences within 30 days occurred in amoxicillin-treated patients whose cultures grew S. aureus 2

Microbiological Considerations

The bacterial profile of lactational mastitis strongly influences antibiotic selection:

• Staphylococcus aureus is the most common causative organism in infective mastitis, followed by coagulase-negative staphylococci and alpha-hemolytic streptococci 1, 2
• S. aureus isolates from mastitis frequently demonstrate resistance to amoxicillin due to beta-lactamase production 3
• Beta-lactamase-resistant penicillins (such as cloxacillin) or penicillin combinations (amoxicillin-clavulanate) show consistently better effectiveness against S. aureus compared to amoxicillin alone 3

Clinical Recommendation Algorithm

If prescribing antibiotics for lactational mastitis:

1. First-line choice: Amoxicillin-clavulanate rather than amoxicillin alone, given the high prevalence of beta-lactamase-producing S. aureus 3, 2

2. Alternative: Cephalexin or cephradine if penicillin allergy is not severe (non-IgE mediated), as these showed equivalent efficacy to amoxicillin in limited trials 1, 2

3. Dosing for amoxicillin if used: 500 mg orally every 8 hours for 7 days 2

4. Consider non-antibiotic management first in mild cases, as effective milk removal and supportive care may be sufficient 1

Safety in Breastfeeding

Amoxicillin is compatible with breastfeeding:

• Classified as Category A (compatible) for breastfeeding 4
• Present in breast milk but considered safe for the nursing infant 4
• Important caveat: Avoid amoxicillin-clavulanate in women at risk of preterm delivery due to very low risk of necrotizing enterocolitis in the fetus 4

Common Pitfalls to Avoid

• Do not use amoxicillin monotherapy empirically without considering local resistance patterns, as treatment failures are documented with S. aureus infections 2
• Do not delay effective milk removal while waiting for antibiotics to work—this remains a cornerstone of management 1
• Do not assume all antibiotics work equally—susceptibility patterns vary significantly between herds/populations, and the same bacterial species may show different resistance profiles in different settings 5