UMEM Educational Pearls

Category: Pharmacology & Therapeutics

Title: Penicillin-Cephalosporin Cross-Reactivity Made Easy

Keywords: penicillin, cephalosporin, allergy, cross-reactivity (PubMed Search)

Posted: 10/7/2014 by Bryan Hayes, PharmD (Emailed: 11/1/2014) (Updated: 11/4/2014)
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The cross-reactivity between cephalosporins and penicillins is significantly lower than the 10% figure many of us learned. In fact, the beta-lactam ring is rarely involved. So, when the warning pops up next time you order ceftriaxone in a penicillin-allergic patient, what should you do?

In a patient with a documented penicillin allergy, here is a simple chart to help determine when a cephalosporin is ok to use:


Common penicillins and cephalosporins with similar side chains include ampicillin/amoxicillin and cephalexin, cefaclor, cephadroxil, and cefprozil.


Campagna JD, et al. The use of cephalosporins in penicillin-allergic patients: a literature review. J Emerg Med 2012;42(5):612-20. [PMID 21742459]

Pichichero ME, et al. Penicillin and cephalosporin allergy. Ann Allergy Asthma Immunol 2014;112:404-12. [PMID 24767695]

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