What is the recommended treatment for mastitis in a pregnant patient?

Treatment of Mastitis in Pregnancy

Dicloxacillin 500 mg orally four times daily or cephalexin 500 mg orally four times daily for 10-14 days are the first-line antibiotics for mastitis during pregnancy, both targeting Staphylococcus aureus with excellent safety profiles and no documented teratogenic effects. 1

First-Line Antibiotic Selection

• Dicloxacillin 500 mg orally four times daily is the preferred first-line agent, targeting methicillin-susceptible Staphylococcus aureus (the predominant pathogen), with minimal milk transfer and no adverse fetal effects reported. 1, 2

• Cephalexin 500 mg orally four times daily is an equally effective alternative, particularly useful for patients with non-severe penicillin allergies, and is endorsed by the American Academy of Pediatrics and CDC as safe during pregnancy. 1, 2

• Both antibiotics allow continued breastfeeding (if already lactating) with drug concentrations in milk that do not produce toxicity in nursing infants. 1

• The usual treatment duration is 10-14 days, though some sources suggest 7 days with adjustment based on clinical response. 2

Alternative Antibiotics for Penicillin Allergy

• Clindamycin 300-450 mg orally three times daily is appropriate for true penicillin-allergic patients, though it has moderate evidence supporting safety in pregnancy and may increase gastrointestinal side effects in breastfeeding infants. 1, 2

• Azithromycin is safe in pregnancy based on studies in non-mastitis patients, though it carries a very low risk of infantile hypertrophic pyloric stenosis if used during the first 13 days of infant life. 1, 2

Antibiotics to Avoid in Pregnancy

• Never use doxycycline, metronidazole, or trimethoprim-sulfamethoxazole (TMP-SMX) during pregnancy due to potential fetal risks. 1

• TMP-SMX specifically poses risks of bilirubin displacement, hyperbilirubinemia, and fetal hemolytic anemia. 3

When to Escalate Care

• Hospitalize immediately if fever and chills persist despite outpatient antibiotics, indicating systemic involvement requiring IV antibiotics. 1

• Provide access to breast pump and lactation support staff during hospitalization. 1

• Consider MRSA coverage (clindamycin, TMP-SMX with beta-lactam, or vancomycin IV) if there is high local MRSA prevalence, previous MRSA infection, or failure to respond to first-line therapy within 48-72 hours. 2, 3

Management of Breast Abscess

• If abscess develops, perform ultrasound-guided needle aspiration as the preferred drainage method over surgical incision. 1

• Continue breastfeeding on the affected side provided the infant's mouth does not contact purulent drainage. 1, 3

Critical Pitfalls to Avoid

• Never discontinue breastfeeding (if already lactating), as this worsens mastitis and increases abscess risk by causing engorgement and blocked ducts. 1, 3

• Avoid overstimulation, excessive pumping, heat application, and aggressive massage, which exacerbate inflammation and tissue injury. 1, 4

• Do not delay antibiotic therapy beyond 12-24 hours if conservative measures fail, as this increases the risk of abscess formation (occurring in approximately 10% of mastitis cases). 3, 4

Special Considerations for Antepartum Mastitis

• Antepartum mastitis is uncommon but requires the same aggressive treatment approach to prevent abscess formation and subsequent lactation difficulties. 5

• Early recognition and adequate antibiotic treatment are key to avoiding complications that can lead to residual scarring and nipple dysfunction. 5