What is the best antibiotic for treating mastitis?

Best Antibiotic for Mastitis

Dicloxacillin or flucloxacillin (500 mg orally four times daily for 7-10 days) are the first-line antibiotic treatments for mastitis, with clindamycin (300-450 mg orally three times daily) as the preferred alternative for penicillin-allergic patients. 1

First-Line Treatment Options

For Non-Allergic Patients:

• Dicloxacillin: 500 mg orally four times daily for 7-10 days 1
• Flucloxacillin: 500 mg orally four times daily for 7-10 days 1

These antibiotics are particularly effective against Staphylococcus aureus, which is the most common causative organism in mastitis 2.

For Penicillin-Allergic Patients:

• Clindamycin: 300-450 mg orally three times daily for 7-10 days 1
• Cephalexin: 500 mg orally four times daily (for non-immediate hypersensitivity reactions) 1

Safety During Breastfeeding

Dicloxacillin has an excellent safety profile during breastfeeding:

• The relative infant dose (RID) is only 0.03% of the maternal dose 3
• High plasma protein binding limits transfer into breast milk 3
• The American Academy of Pediatrics recommends continuing breastfeeding during antibiotic treatment 1

MRSA Considerations

If there's no response to initial therapy or if MRSA is suspected:

• Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily 1
• Vancomycin: 1-2 g IV every 8 hours (for severe infections requiring hospitalization) 1
• Linezolid: May be considered for MRSA mastitis, though the relative infant dose is higher at 15.61% (still below therapeutic doses for infants) 4

Treatment Algorithm

1. Initial Assessment:

   • Evaluate severity (focal tenderness, fever, malaise)
   • Determine if abscess is present (requires drainage)

2. First-Line Treatment:

   • No penicillin allergy → Dicloxacillin or flucloxacillin
   • Penicillin allergy → Clindamycin or cephalexin (if non-immediate hypersensitivity)

3. If No Improvement After 48-72 Hours:

   • Consider MRSA → Switch to trimethoprim-sulfamethoxazole
   • Obtain milk culture if not done initially
   • Evaluate for abscess formation

4. Supportive Measures (essential component of treatment):

   • Continue breastfeeding for effective milk removal 5
   • Apply warm compresses before feeding
   • Ensure proper breastfeeding technique

Important Caveats

• Continued breastfeeding is crucial for effective treatment and does not pose a risk to the infant 2
• Breast abscess is the most common complication and can be prevented by early treatment and continued breastfeeding 2
• If abscess occurs, surgical drainage or needle aspiration is needed while continuing breastfeeding 2
• Amoxicillin-clavulanate (875/125 mg PO every 12 hours) is another option with broader coverage when mixed infections are suspected 1

The Infectious Diseases Society of America emphasizes identifying the likely pathogen, considering local resistance patterns, and selecting the narrowest spectrum agent effective against the suspected pathogen 1.