What is the recommended treatment for mastitis in a lactating adult woman?

Treatment of Lactational Mastitis

Begin with a 1-2 day trial of conservative management (NSAIDs, ice, continued breastfeeding) before initiating antibiotics, and if antibiotics become necessary, use dicloxacillin 500 mg orally four times daily or cephalexin 500 mg orally four times daily as first-line agents. 1

Initial Conservative Management (First 12-24 Hours)

• Start with non-antibiotic measures for 1-2 days, as 14-20% of mastitis cases resolve spontaneously and most are inflammatory rather than infectious 1
• Administer NSAIDs for pain and inflammation 1
• Apply ice to the affected breast 1
• Continue breastfeeding from the affected breast, as regular breast emptying is essential for resolution and does not pose risk to the infant 1, 2
• Avoid excessive pumping, aggressive breast massage, and heat application, as these may worsen the condition by overstimulating milk production and causing tissue trauma 3

When to Initiate Antibiotics

Add antibiotics if symptoms do not improve within 12-24 hours of conservative management, as delaying treatment risks abscess formation, which occurs in approximately 10% of mastitis cases 1, 2

First-Line Antibiotic Therapy

For Methicillin-Susceptible S. aureus (Most Common)

• Dicloxacillin 500 mg orally four times daily is the preferred agent 1, 2
• Cephalexin 500 mg orally four times daily is an equally effective alternative, particularly useful for penicillin-allergic patients 1, 2
• Both agents are safe during breastfeeding with minimal transfer to breast milk 1

For Penicillin-Allergic Patients (Non-Severe Allergy)

• Cephalexin 500 mg orally four times daily remains an option 1
• Erythromycin or azithromycin are alternatives, but avoid macrolides during the first 13 days of infant life due to very low risk of infantile hypertrophic pyloric stenosis 2

MRSA Coverage (When Indicated)

Consider MRSA-active antibiotics if:

• High local MRSA prevalence exists 1, 2
• Patient has previous MRSA infection 1, 2
• No response to first-line beta-lactam antibiotics within 48-72 hours 1

MRSA-Active Antibiotic Options

• Clindamycin 300-450 mg orally three times daily (use with caution as it may increase GI side effects in the infant) 2
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets orally twice daily, but avoid in infants ≤28 days old or those with jaundice, prematurity, or G6PD deficiency due to risk of bilirubin displacement and hyperbilirubinemia 1, 2
• If using TMP-SMX, add a concurrent beta-lactam if streptococcal infection is possible, as TMP-SMX lacks activity against Streptococcus species 2

Severe Cases Requiring Hospitalization

Admit patients with systemic symptoms suggesting sepsis risk, such as fever and chills 1, 4

Intravenous Antibiotic Options

• Vancomycin 1 g IV every 12 hours for severe mastitis 2
• Cefazolin 2 g IV loading dose, then 1 g IV every 8 hours for penicillin-allergic patients requiring parenteral treatment 2
• Linezolid 600 mg IV twice daily as an alternative MRSA-active agent 2
• Daptomycin 4 mg/kg IV once daily may be used for severe cases 2

Supportive Care During Treatment

• Continue breastfeeding throughout antibiotic therapy, as this helps resolve the mastitis and does not pose risk to the infant 1, 2, 4
• Provide pain management with appropriate analgesics 4
• If hospitalization occurs, provide access to a breast pump if prolonged separation from infant is necessary 4

Monitoring and Follow-Up

• Reevaluate within 48-72 hours if symptoms worsen or do not improve to rule out abscess formation 2
• Consider obtaining milk cultures to guide antibiotic therapy, particularly in immunocompromised patients or those with recurrent symptoms 3
• Perform ultrasound if abscess is suspected 3

Management of Breast Abscess (10% Complication Rate)

• Breast abscess requires surgical drainage or needle aspiration 2, 5
• Breastfeeding can continue on the affected side as long as the infant's mouth does not contact purulent drainage from the breast 4

Red Flags Requiring Urgent Evaluation

Symptoms persisting beyond 1 week of appropriate antibiotics may indicate inflammatory breast cancer, particularly in non-lactating women, and warrant urgent evaluation with ultrasound and possible biopsy within 48 hours 1