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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