What are the first-line antibiotic recommendations for mastitis in the UK?

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Last updated: June 4, 2025View editorial policy

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From the Research

The first-line antibiotic recommendation for mastitis in the UK is flucloxacillin 500mg four times daily for 10-14 days. This is the preferred treatment because Staphylococcus aureus is the most common causative organism in mastitis, and flucloxacillin specifically targets this bacterium 1. For patients with penicillin allergy, clarithromycin 500mg twice daily for 10-14 days or erythromycin 250-500mg four times daily for 10-14 days are appropriate alternatives.

Key Considerations

  • Treatment should be started promptly after diagnosis, and patients should be advised to continue breastfeeding or expressing milk from the affected breast to prevent milk stasis, which can worsen the infection.
  • Adequate pain relief with paracetamol or ibuprofen is also recommended, along with rest, increased fluid intake, and warm compresses to the affected breast before feeding to help with milk flow.
  • If symptoms do not improve within 48 hours of starting antibiotics, or if the patient develops systemic symptoms such as high fever or feels significantly unwell, they should seek further medical advice as they may need intravenous antibiotics or surgical drainage if an abscess has formed.

Alternative Treatments

  • Although some studies suggest the use of Lactobacilli isolated from breast milk as an alternative to antibiotics for treating infectious mastitis during lactation 2, the current evidence is not strong enough to support this as a first-line treatment.
  • The most recent and highest quality study available 1 supports the use of flucloxacillin as the first-line antibiotic treatment for mastitis in the UK.

Important Notes

  • It is essential to note that the evidence for antibiotic treatment of mastitis is limited, and more research is needed to determine the most effective treatment strategies 3.
  • However, based on the current evidence and clinical guidelines, flucloxacillin remains the recommended first-line antibiotic treatment for mastitis in the UK.

References

Research

Treatment of infectious mastitis during lactation: antibiotics versus oral administration of Lactobacilli isolated from breast milk.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2010

Research

Antibiotics for mastitis in breastfeeding women.

The Cochrane database of systematic reviews, 2013

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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