EBQ:Cephalosporin Cross-reactivity

Prior to 1980, penicillins(PCN) and cephaloporins were often produced using the same fungus and the chance for contamination during the manufacturing process of a cephalosporin with a PCN was high. The allergy was assumed to be due to the beta-lactam ring but was later determined to be due to the manufacturing process.

More recent studies have determined that the actual risk of cross-reactivity relates to side chain similarity and not the beta-lactam ring. 1st and 2nd generation penicillins share the same R-1 side chain and are more likely to exhibit cross reactivity. A current review of the literature demonstrates that the 10% or greater allergy that is commonly reported may be exaggerated.

• 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%.
• Overall cross-reactivity rate in patients with a confirmed penicillin allergy = 2.5%.
• Cross-reactivity between penicillins and 1st and 2nd generation cephalosporins is possible.
• 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.

Sources

http://www.ncbi.nlm.nih.gov/pubmed?term=21742459