What is the first-line antibiotic treatment for mastitis?

First-Line Antibiotic Treatment for Mastitis

For lactational mastitis requiring antibiotic therapy, dicloxacillin 500 mg four times daily orally is the first-line treatment, with cephalexin 500 mg four times daily as an alternative for penicillin-allergic patients (except those with immediate hypersensitivity reactions). 1, 2

When to Initiate Antibiotics

• Start with a 1-2 day trial of conservative management first (NSAIDs, ice application, continued breastfeeding from the affected breast, minimizing pumping) before prescribing antibiotics 3
• Antibiotics are indicated if symptoms do not improve after 24-48 hours of conservative measures, or if the patient presents with severe symptoms initially 2, 3
• Most mastitis cases are inflammatory rather than infectious, making immediate antibiotic therapy unnecessary in many cases 3

First-Line Antibiotic Options

Preferred agents (target Staphylococcus aureus):

• Dicloxacillin 250-500 mg orally four times daily 1, 2
• Cephalexin 250-500 mg orally four times daily 1, 2

Alternative agents:

• Clindamycin 300-450 mg orally three times daily (for penicillin allergy with immediate hypersensitivity) 1
• Erythromycin 250 mg orally four times daily (though some strains may be resistant) 1

Duration and Monitoring

• Standard treatment duration is 10-14 days 2
• Continued breastfeeding from the affected breast should be strongly encouraged and does not pose risk to the infant 2, 3
• Dicloxacillin transfers minimally into breast milk (relative infant dose only 0.03%), making it safe for breastfeeding 4

Important Clinical Considerations

Obtain milk cultures when:

• Symptoms worsen despite antibiotic therapy 3
• Recurrent mastitis occurs 3
• Patient is immunocompromised 3
• This guides antibiotic selection, particularly with rising methicillin-resistant S. aureus (MRSA) prevalence 2

Perform ultrasonography if:

• Symptoms worsen or fail to improve after 48-72 hours of appropriate antibiotic therapy 3
• Recurrent episodes occur 3
• Patient is immunocompromised 3
• This identifies breast abscess formation, which requires drainage 2, 5

Practices to Avoid

• Do not recommend excessive pumping, aggressive breast massage, or heat application - these worsen mastitis by overstimulating milk production and causing tissue trauma 3
• Avoid azithromycin and oral third-generation cephalosporins as first-line agents due to S. pneumoniae resistance concerns in other contexts 1
• Probiotics lack sufficient evidence for treatment or prevention 3

Escalation of Care

Consider hospital admission with IV antibiotics if:

• Patient develops sepsis or systemic toxicity 3
• Oral therapy fails after 48-72 hours 2
• Breast abscess requires surgical drainage 2, 5

For IV therapy, use:

• Nafcillin or oxacillin 1-2 g every 4 hours IV (for methicillin-susceptible S. aureus) 1
• Vancomycin 30 mg/kg/day in 2 divided doses IV (for MRSA or severe penicillin allergy) 1