Antibiotics for Mastitis

Choice of antibiotic[12]- It is important to review the sensitivity patterns of bacteria in your local area or health authority.

Cephalexin (Keflex®), Cloxacillin and Clindamycin

For treatment of symptoms consistent with mastitis for more than 24 hours. If the symptoms are worsening (increased pain, spreading of the redness, enlargement of the hardened area) for less than 24 hours, it is reasonable to start the antibiotics sooner. Whether mastitis is resolving with or without antibiotic treatment, symptoms should progressively resolve and should have disappeared over 2 to 5 days. Fever will usually be gone within 24 hours, the pain within 24 to 48 hours, and the breast hardness within the next few days. The redness may remain for a week or longer.

Breastfeeding should continue through the treatment of mastitis, even when on antibiotics as these are considered safe in breastfeeding. Continuation of breastfeeding is considered safe and is encouraged.

Cephalexin or Cloxacillin – both about equally effective.
Cloxacillin may be used if there is no allergy to penicillin.
Cephalexin may be used if there is a rash-only reaction to penicillin as the chance of cross-reaction is only about 3%.
Cloxacillin and cephalexin should be avoided if there is a serious allergy to penicillin (anaphylaxis; hives; throat edema; bronchoconstriction; serum sickness; hemolytic anemia; exfoliative dermatitis; organ dysfunction).

Clindamycin may be used if there is a serious penicillin allergy as above, or as a second choice if the infection is unresponsive to either cephalexin or cloxacillin.

The overall rate of susceptibility of Staph aureus to these three antibiotics is about the same, around 80%, however clindamycin is effective in about 75% of the methicillin-resistant bacteria (MRSA). Check local resistance patterns.

12. Dixon, J.M. (2012). Lactational Mastitis. Retrieved from

Cephalexin (Keflex®)