EBQ:Cephalosporin Cross-reactivity

Revision as of 17:52, 5 October 2013 by Ostermayer (talk | contribs)

Prior to 1980, penicillins and cephaloporins were often produced using the same fungus and the chance for contamination during the manufacturing process was high. The belief was that the beta-lactam ring similarities must be the cause. How wrong we were.

More recent studies have determined that the actual risk of cross-reactivity relates more to a side chain similarity and probably not the beta-lactam ring at all. Therefore it makes sense that if a penicillin and a cephalosporin share that particular (R-1) side-chain similarity, the risk of cross-reactivity is increased. Such is the case with amoxicillin or ampicillin with:

  • 1st generation cephalosporins: cefadroxil, cefatrizine, cephalexin, cephradine
  • 2nd generation cephalosporins: cefaclor, cefprozil

Campagna Review Article

  • Overall cross-reactivity rate between cephalosporins and penicillins in patients reporting a penicillin allergy = 1%. [1]
  • Overall cross-reactivity rate in patients with a confirmed penicillin allergy = 2.5%.
  • Cross-reactivity between penicillins and MOST 1st and 2nd generation cephalosporins is negligible.
  • Cross-reactivity between penicillins and ALL 3rd and 4th generation cephalosporins is negligible.
  • If a patient has an allergy to amoxicillin or ampicillin, avoid cefadroxil, cefaclor, cefatrizine, cefprozil, cephalexin, and cephradine.


  1. Campagna JD, Bond MC, Schabelman E, Hayes BD. The use of cephalosporins in penicillin-allergic patients: A literature review. J Emerg Med. 2012;42(5):612-20