What are the recommended antibiotics for treating mastitis in lactating women, and how should I adjust treatment for those with penicillin allergies?

Recommended antibiotics for treating mastitis in lactating women:

• First-line treatment is flucloxacillin, as it is effective against beta-lactamase producing organisms, particularly Staphylococcus aureus, the most common pathogen in mastitis.
• For women with a penicillin allergy, erythromycin or clarithromycin are recommended alternatives. Erythromycin is considered safe in breastfeeding due to low levels in breast milk. Clarithromycin is generally acceptable but should be used only if the benefits outweigh risks, according to the manufacturer; however, LactMed supports its use in breastfeeding women.
• The typical duration of antibiotic treatment is 10–14 days to reduce relapse risk.
• If symptoms do not improve after 48 hours of first-line treatment, consider alternative diagnoses or referral, and if infection persists, prescribe co-amoxiclav as a second-line antibiotic for 10–14 days. For penicillin-allergic women requiring second-line treatment, a combination of clarithromycin or erythromycin plus metronidazole is recommended to cover anaerobic bacteria.

These antibiotics are acceptable in breastfeeding women as the low levels in breast milk are unlikely to cause adverse effects in the infant.