Antibiotics for Lactational Mastitis

Based on Guidelines on the Treatment, Management & Prevention of Mastitis by GAIN2.

What is Mastitis?

Mastitis is an inflammation the breast tissue. It is a quite common condition in breastfeeding or lactating women and is also called lactational mastitis ("milk fever").


Mastitis usually occurs when ineffectively removed milk plugs the milk duct. Lactational mastitis is often bacterial, because stagnant milk provides an environment for bacterial growth. However, how infection enters a breast is uncertain.

Staphylococcus aureus is the major pathogenic bacteria of mastitis. Less common infecting organisms are Streptococcus or Escherichia coli.

The main indicative symptoms of mastitis are hard, warm, red, tender, swollen area of one breast.

best antibiotics for mastitis infographic

Mastitis Treatment

The most important step in the management of mastitis is prompt removal of milk. Without effective milk removal, non-infectious mastitis is likely to progress to infectious mastitis, and infectious mastitis to the formation of an abscess. On the other hand breast emptying promotes more rapid symptom relief with antibiotics.

It is important to understand that the infection is not in the breast milk itself. So mastitis does not necessitate cessation of breastfeeding. In fact, women who wean while they have mastitis are a greater risk for abscess3.

Mastitis may improve all on its own with breast emptying, heat, and rest. Antibiotic treatment may be started if symptoms don't improve within 12 to 24 hours or in cases of severe symptoms (painful lump in the breast, heat, redness). Antibiotic for mastitis should be active against Staphylococcus aureus.

If left untreated the condition may progress to the formation of a breast abscess. Breast abscess is a localized collection of pus in the breast.

Best Antibiotics for Mastitis

Antibiotics used in the treatment of mastitis should:

  • be secreted in milk and achieve good concentrations in milk
  • retain activity in acidic pH of milk
  • be compatible with breast feeding.

Improvement of symptoms is usually noted within 2 to 3 days of treatment. If improvement is very slow, milk should be collected for culture and sensitivity.

Important note: The use of antibiotic does not generally necessitate suspension or cessation of breastfeeding, because these drugs are safe to take during lactation.

Antibiotic therapy should be continued for at least 5 days. However, many medical authorities recommend a 10-14-day course of antibiotics for mastitis.

Dicloxacillin and Flucloxacillin for Mastitis

Flucloxacillin and dicloxacillin are the antibiotics of choice for mastitis according treatment guidelines1, 2.

Both Flucloxacillin and Dicloxacillin are narrow-spectrum penicillins. And both are active against beta-lactamase-producing Staphylococcus aureus and are indicated for soft tissue infections caused by S. aureus.

Dicloxacillin is a prototype of antistaphylococcal penicillins. Dicloxacillin is similar in antibacterial activity, pharmacologic properties, and indications to flucloxacillin, and these two agents are considered interchangeable.

Dicloxacillin appears to have a lower rate of hepatic side effects than flucloxacillin. Unlike flucloxacillin, dicloxacillin does not have cautions about the risk of liver toxicity4.

On the other hand, intravenous dicloxacillin is more likely to cause phlebitis (inflammation of a vein) than intravenous flucloxacillin.

Both antibiotics are compatible with breastfeeding. Small amounts of flucloxacillin or dicloxacillin are excreted into breast milk but the concentration is probably too low to have a significant effect on the breastfed infant.

  • Flucloxacillin dosage: 500 mg 4 times per day for 5-14 days.
  • Dicloxacillin dosage: 125-500 mg 4 times per day for 5-14 days.

Erythromycin for Mastitis

Erythromycin is considered the drug of choice because it has high efficacy, low cost, and low risk of inducing bacterial resistance. Erythromycin is well concentrated and remains active in breast milk.

Erythromycin may be useful for breast infections caused by methicillin-resistant Staphylococcus aureus (CA-MRSA)5. Erythromycin is also a choice for women allergic to penicillin antibiotics.

Erythromycin dosage for mastitis: 500 mg 4 times per day for 5-14 days.

Cephalexin (Keflex®) for Mastitis

Cephalexin, a first-generation cephalosporin antibiotic is also acceptable first-line treatment, but may be less preferred because of its broader antimicrobial spectrum.

Cephalexin is usually prescribed for mastitis in women with hypersensitivity to penicillins (excluding immediate hypersensitivity). Cephalexin is excreted into breast milk in small amounts and it is unlikely to have a negative effect on the breastfed baby.

Cephalexin is highly effective antibiotic for the treatment of streptococcal and staphylococcal skin infections, comparable to erythromycin, clindamycin, dicloxacillin, cloxacillin 7.

Cephalexin dosage: 500 mg 4 times a day for at least 5 days.

Why cephalexin is not a first line choice? Because cephalexin has a broader spectrum of activity than flucloxacillin or dicloxacillin, so it is more likely to contribute to gram-negative resistance. Therefore it is recommended to use dicloxacillin instead of cephalexin for skin and soft tissue infections like mastitis.

Clindamycin (Cleocin®) for Mastitis

Clindamycin is used as a second choice in woman who cannot tolerate usual medications. Clindamycin is a good option for women with severe penicillin allergy, for infections unresponsive to either dicloxacillin or cephalexin. It may also treat MRSA infections6.

Clindamycin dosage: 300 mg 4 times daily for 5-14 days.

Amoxicillin, Amoxicillin/Clavulanate for Mastitis

Although amoxicillin may provide symptom relief and abscess formation it is not the best antibiotic for mastitis. Amoxicillin is not effective against beta-lactamase-producing S. aureus10. Amoxicillin/clavulanate is a more effective treatment choice.

Amoxicillin and combination of amoxicillin with clavulanic acid are considered safe during lactation9.

Amoxicillin dosage: 250-500 mg every 8 hours. Antibiotics should be continued for 10 days to reduce systemic infection and local cellulitis.

Amoxicillin/clavulanate (Augmentin®) dosage: 875 mg twice daily for 10 days.


Other antibiotics

Trimethoprim/Sulfamethoxazole (Bactrim®) for Mastitis

Trimethoprim with Sulfamethoxazole, also known as co-trimoxazole, may be an alternative treatment against Methicillin-Resistant Staphylococcus aureus8. It is excreted into breast milk and is and unlikely to cause any serious side effects in the breastfed baby.

Trimethoprim/Sulfamethoxazole should be avoided in women breast-feeding healthy infants aged 2 months or younger and compromised infants.

Trimethoprim/Sulfamethoxazole dosage: 160 mg/800 mg twice daily.

Doxycycline for Mastitis

Doxycycline is active against Staphylococcus aureus, including MRSAs trains. However, doxycycline should not be used if woman is breastfeeding.

How long to take antibiotic for mastitis?

Antibiotic therapy is usually continued for 5-14 days to avoid relapse. Relapsing mastitis is more difficult to cure.

When to expect an improvement?

Whether mastitis is resolving with or without antibiotic, symptoms should progressively subside and disappear over 2 to 5 days.

Fever usually is gone within 24 hours, the pain within 24 to 48 hours, and the breast hardness and swelling within the next few days.

Further reading


  • 1. Spencer JP. Management of Mastitis in Breastfeeding Women. Am Fam Physician. 2008 Sep 15;78(6):727-731.
  • 2. Guidelines on the Treatment, Management & Prevention of Mastitis. Guidelines & Audit Implementation Network.
  • 3. Lawrence, R. A., Lawrence, R. M. Breastfeeding: A Guide for the Medical Profession, 6th ed., 2005 Mosby
  • 4. Adverse Drug Reactions Advisory Committee. A comparison of dicloxacillin with flucloxacillin. Australian Adverse Drug Reactions Bulletin. 1999; 18 (2).
  • 5. Chuwa EW, Wong CM, Tan YY, Hong GS. MRSA breast abscesses in postpartum women. Asian J Surg. 2009 Jan;32(1):55-8.
  • 6. Boccaccio C, Verdaguer Babic V, Botto L, et al. Methicillin-resistant Staphylococcus aureus (MRSA) isolation in breast abscesses in a Public Maternity. Medicina (B Aires). 2014;74(3):210-5.
  • 7. Derrick CW Jr, Reilly K. The role of cephalexin in the treatment of skin and soft-tissue infections. Postgrad Med J. 1983;59
  • 8. Boccaccio C, VerdaguerBabic V, Botto L, et al. Methicillin-resistant Staphylococcus aureus (MRSA) isolation in breast abscesses in a Public Maternity. Medicina (B Aires). 2014;74(3):210-5.
  • 9. Benyamini L, Merlob P, Stahl B, et al. The safety of amoxicillin/clavulanic acid and cefuroxime during lactation. Ther Drug Monit. 2005 Aug;27(4):499-502. PubMed
  • 10. Hager WD, Barton JR. Treatment of sporadic acute puerperal mastitis. Infect Dis Obstet Gynecol. 1996;4(2):97-101. PubMed

Published: April 09, 2019
Last updated: April 09, 2019



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