What antibiotics are recommended for a lactating woman with mastitis?

Antibiotics for Mastitis in Lactating Women

First-Line Antibiotic Recommendations

For lactational mastitis, dicloxacillin 500 mg orally four times daily or cephalexin 500 mg orally four times daily are the recommended first-line antibiotics, targeting methicillin-susceptible Staphylococcus aureus which causes the majority of infectious mastitis cases. 1

Primary Treatment Options

• Dicloxacillin 500 mg orally four times daily is the oral agent of choice for methicillin-susceptible S. aureus according to the Infectious Diseases Society of America 1
• Cephalexin 500 mg orally four times daily is an equally effective alternative, particularly useful for penicillin-allergic patients 1
• Both antibiotics are considered compatible with breastfeeding, with minimal transfer to breast milk 1

Broad-Spectrum Alternative

• Amoxicillin/clavulanic acid serves as a broad-spectrum option that is safe during breastfeeding based on limited human data 1, 2
• This combination is classified as FDA Category B and explicitly compatible with nursing 2

Treatment Approach and Breastfeeding Continuation

Continued breastfeeding during antibiotic treatment is essential and does not pose a risk to the infant—in fact, it helps resolve the mastitis. 1

• Regular breast emptying through continued breastfeeding is crucial for mastitis resolution 1, 3
• Approximately 10% of mastitis cases progress to breast abscess if not properly treated, making continued milk removal a key component of therapy 1, 4
• Premature cessation of breastfeeding causes more harm, including risks of breast engorgement, blocked ducts, and worsening mastitis 1

MRSA Coverage Considerations

When methicillin-resistant S. aureus is suspected, adjust antibiotic selection:

• Consider MRSA coverage if local MRSA prevalence is high, there is previous MRSA infection, or no response to first-line therapy 1
• Clindamycin is an option for suspected or confirmed MRSA, though use with caution as it may increase GI side effects in the infant 1, 2
• As MRSA becomes more common, antibiotics effective against this organism may become preferred 4

Penicillin-Allergic Patients

For women with penicillin allergies:

• Erythromycin or azithromycin are acceptable alternatives 1, 2
• Important caveat: There is a very low risk of infantile hypertrophic pyloric stenosis in infants exposed to macrolides during the first 13 days of breastfeeding, but this risk does not persist after 2 weeks 1, 2
• Macrolides are generally considered safe after the first 13 days of infant life 1

Monitoring and Follow-Up

If symptoms worsen or do not improve within 48-72 hours of starting antibiotics, reevaluation is necessary to rule out an abscess. 1

• Consider alternative antibiotics based on culture results if initial therapy fails 1
• Breast abscess occurs in approximately 10% of mastitis cases and is the most common complication 1, 4
• All breastfed infants should be monitored for gastrointestinal effects due to alteration of intestinal flora 2

Antibiotics to Avoid

• Tetracyclines and fluoroquinolones should generally be avoided due to potential impacts on the baby's development 1, 3
• If tetracyclines are necessary, limit doxycycline use to 3 weeks maximum without repeating courses 2

Common Pitfalls to Avoid

• Never advise expressing and discarding breast milk during mastitis treatment—this is illogical and risks breast engorgement, blocked ducts, and worsening mastitis 1
• Do not delay antibiotic treatment beyond 12-24 hours if conservative management (frequent breast emptying) fails, as this risks abscess formation 1
• Ensure proper breastfeeding technique with assistance from a lactation consultant, as poor positioning can precipitate mastitis 4