What is the antibiotic of choice for treating mastitis?

Antibiotic of Choice for Mastitis

For mastitis in breastfeeding women, dicloxacillin or cephalexin are the first-line antibiotics of choice due to their effectiveness against Staphylococcus aureus, the most common causative organism. 1

Causative Organisms and Antibiotic Selection

• Staphylococcus aureus is the predominant pathogen in mastitis, requiring antibiotics that provide adequate coverage against this organism 1
• First-line antibiotic options include:
  • Dicloxacillin 500 mg orally four times daily 1
  • Cephalexin 500 mg orally four times daily 1
• These penicillinase-resistant antibiotics are specifically effective against the beta-lactamase-producing S. aureus commonly found in mastitis 2

Treatment Algorithm

For Uncomplicated Mastitis:

1. First-line therapy:

   • Dicloxacillin 500 mg orally four times daily for 7-10 days 1
   • OR Cephalexin 500 mg orally four times daily for 7-10 days 1

2. For penicillin-allergic patients:

   • Clindamycin 300-450 mg orally three times daily 2

3. If MRSA is suspected or confirmed:

   • Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily 2
   • OR Clindamycin 300-450 mg orally three times daily 2

For Severe or Complicated Mastitis:

1. Consider parenteral therapy:
   • Oxacillin or nafcillin 1-2 g IV every 4-6 hours 2
   • OR Cefazolin 1 g IV every 8 hours 2
   • OR Vancomycin 15 mg/kg IV every 12 hours (if MRSA suspected) 2

Important Clinical Considerations

• Continued breastfeeding should be encouraged during treatment as it helps with breast emptying and does not pose a risk to the infant 1
• Frequent, complete emptying of the breast is essential for treatment success and prevention of complications 1
• Consultation with a lactation specialist may be beneficial to optimize breastfeeding technique 1
• The most common complication of mastitis is breast abscess, which requires surgical drainage or needle aspiration if it develops 1

Special Situations

• As methicillin-resistant S. aureus (MRSA) becomes more common in the community, it may be an increasingly frequent cause of mastitis 1
• For suspected or confirmed MRSA infections, appropriate antibiotics include TMP-SMX, clindamycin, or linezolid, depending on local susceptibility patterns 2, 3
• For patients with severe beta-lactam allergies, clindamycin is the preferred alternative if the organism is susceptible 2

Common Pitfalls and Caveats

• Failure to continue breastfeeding during treatment may worsen symptoms and lead to abscess formation 1
• Inadequate breast emptying can lead to treatment failure 1
• Sore nipples can precipitate mastitis and should be addressed as part of treatment 1
• Empiric antibiotic therapy should always cover S. aureus as the most likely pathogen 1
• Delayed treatment can lead to complications including abscess formation requiring surgical intervention 1