A 32-year-old mother at 2 weeks postpartum develops acute mastitis with fever, localized breast erythema, and purulent discharge. She is breastfeeding and wishes to continue. What is the drug of choice for treating mastitis while preserving lactation?

Explanation

## Antibiotic Management of Postpartum Mastitis **Key Point:** Beta-lactam antibiotics (flucloxacillin or cephalexin) are the first-line agents for lactation-preserving mastitis treatment because they are effective against *Staphylococcus aureus*, safe in breast milk, and allow continued breastfeeding. ### Pathophysiology of Mastitis Mastitis typically results from milk stasis and bacterial colonization (most commonly *Staphylococcus aureus*, including MRSA in some settings). Continued milk removal (breastfeeding or expression) is essential to prevent abscess formation and is compatible with appropriate antibiotic therapy. ### First-Line Antibiotic Regimens | Agent | Spectrum | Breast Milk Safety | Dosing | Notes | |-------|----------|-------------------|--------|-------| | **Flucloxacillin** | *S. aureus* (including MSSA) | Safe | 500 mg QID × 10–14 days | Preferred in UK/Commonwealth | | **Cephalexin** | *S. aureus*, Gram-positive | Safe | 500 mg QID × 10–14 days | First-generation cephalosporin; preferred in US | | **Amoxicillin-clavulanate** | Broader spectrum | Safe | 875/125 mg BD × 10–14 days | Alternative if MRSA coverage needed | | **Tetracycline** | Broad | **NOT safe** | — | Deposits in bone/teeth; contraindicated | | **Metronidazole** | Anaerobes | Minimal evidence | — | No role in mastitis (not anaerobic) | **High-Yield:** The combination of **beta-lactam antibiotic + continued breastfeeding + supportive care (analgesia, heat, milk removal)** is the gold standard and prevents 90% of abscess formation. ### Adjunctive Management 1. **Milk removal:** Continue breastfeeding or express milk regularly 2. **Analgesia:** Paracetamol or ibuprofen (safe in lactation) 3. **Local measures:** Warm compresses, breast support 4. **Duration:** Antibiotics for 10–14 days; clinical improvement expected by 48–72 hours **Clinical Pearl:** If mastitis does not resolve within 48–72 hours of appropriate antibiotics, suspect **breast abscess** and obtain ultrasound for drainage consideration. ### MRSA Considerations If MRSA is suspected or confirmed (e.g., healthcare-associated infection): - **First-line:** Trimethoprim-sulfamethoxazole (TMP-SMX) or clindamycin - **Avoid:** Fluoroquinolones (limited data in lactation) **Warning:** Do NOT use tetracyclines, fluoroquinolones, or metronidazole as first-line agents in lactating women; they either concentrate in breast milk or lack evidence of safety. [cite:RCOG Green-top Guideline 64; Williams Obstetrics 26e Ch 37]