What is the appropriate management of acute lactational mastitis in a breastfeeding woman, including first‑line antibiotic choice, supportive care, and criteria for escalation or referral?

Management of Acute Lactational Mastitis

Initial Conservative Management (First 12-24 Hours)

Start with a 1-2 day trial of conservative measures before initiating antibiotics, as 14-20% of mastitis cases resolve spontaneously and most are inflammatory rather than infectious. 1

Conservative Measures Include:

• NSAIDs for pain and inflammation control 1
• Ice application to the affected breast 1
• Continued breastfeeding or milk expression from the affected breast – this is essential for resolution and should never be interrupted 1, 2
• Avoid excessive pumping, heat application, and aggressive breast massage – these worsen inflammation by overstimulating milk production and causing tissue trauma 3

Critical Pitfall to Avoid:

Do not advise expressing and discarding breast milk, as this is counterproductive and risks worsening engorgement, blocked ducts, and mastitis progression 4. The infant can safely breastfeed from the affected breast. 2

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Antibiotic Therapy (If No Improvement in 12-24 Hours)

If symptoms do not improve within 12-24 hours of conservative management, initiate narrow-spectrum antibiotics targeting Staphylococcus aureus, which causes the majority of infectious mastitis cases. 1

First-Line Antibiotic Options:

Dicloxacillin 500 mg orally four times daily is the preferred agent for methicillin-susceptible S. aureus 1, 4

OR

Cephalexin 500 mg orally four times daily is equally effective and particularly useful for penicillin-allergic patients 1, 4

• Both agents are safe during breastfeeding with minimal transfer to breast milk 1
• Typical treatment duration is 10-14 days 5

Alternative Antibiotics:

• Amoxicillin/clavulanic acid – broad-spectrum option, safe during breastfeeding 4
• Erythromycin or azithromycin – for penicillin-allergic patients, but note very low risk of infantile hypertrophic pyloric stenosis if used during first 13 days of infant life 4

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MRSA Coverage (When to Escalate)

Consider MRSA-targeted therapy if:

• High local MRSA prevalence 1
• Previous MRSA infection 1
• No improvement within 48-72 hours of first-line beta-lactam antibiotics 1, 4

MRSA-Targeted Options:

• Clindamycin 300-450 mg orally three times daily (may increase GI side effects in infant) 4
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets orally twice daily – avoid in infants ≤28 days old or those with jaundice, prematurity, or G6PD deficiency due to bilirubin displacement risk 1, 4
  • If using TMP-SMX, add a beta-lactam for streptococcal coverage 4

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Criteria for Hospitalization and IV Antibiotics

Admit to hospital if:

• Fever with chills suggesting systemic involvement or sepsis risk 1, 2
• Worsening symptoms despite oral antibiotics 2
• Immunocompromised status 3

Inpatient IV Antibiotic Regimens:

• Vancomycin 1 g IV every 12 hours for severe MRSA or sepsis concern 4
• Cefazolin 2 g IV loading dose, then 1 g IV every 8 hours for non-severe penicillin allergy 4
• Clindamycin 600 mg IV every 8 hours as alternative MRSA coverage 4

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Imaging and Abscess Evaluation

Obtain breast ultrasound if:

• Symptoms worsen or fail to improve within 48-72 hours of appropriate antibiotics 4, 3
• Palpable mass persists 3
• Immunocompromised patient 3

Breast abscess occurs in approximately 10% of mastitis cases and requires drainage (needle aspiration or surgical) in addition to antibiotics. 1, 2, 5 Breastfeeding can continue on the affected side as long as the infant's mouth does not contact purulent drainage. 2

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Red Flags Requiring Urgent Evaluation

Refer urgently (within 48 hours) for imaging ± biopsy if:

• Symptoms persist beyond 1 week of appropriate antibiotics – may indicate inflammatory breast cancer 1
• Erythema occupying at least one-third of breast surface 1
• Peau d'orange appearance 1

This is particularly critical as inflammatory breast cancer can mimic mastitis, especially in non-lactating women, though it remains rare. 1

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Supportive Care Throughout Treatment

• Pain management with analgesics is essential as pain exacerbates symptoms 2
• Lactation consultant referral to optimize infant latch and breastfeeding technique 5
• Emotional support and reassurance to prevent premature breastfeeding cessation 6
• Ensure access to breast pump if hospitalization causes prolonged separation from infant 2