True Penicillin Allergy or Awaiting Testing/Assessment

What if a patient is truly allergic to penicillin or awaiting an oral challenge test or assessment by an allergist?

• Ideally all patients who report this should be seen by an allergist to assess the potential allergy. If a patient has a history of an IgE-mediated reaction to penicillin, the assumed rate of cross-reacting allergies to cephalosporins is 1-3%

• The risk increases with cephalosporins that have similar side chains to penicillin or amoxicillin, such as cephalexin (Keflex (TM) and Cefoxitin IV); therefore, cephalosporins that are appropriate for substitution include cefazolin (but not oral cephalexin) or cefuroxime, which provide similar antimicrobial coverage

• As such, cefazolin can be given for surgical prophylaxis unless one has had a severe cutaneous adverse reaction (e.g. SJS) or an organ specific side effect (e.g. nephritis) or prior allergy to cefazolin itself

• If one usually gives ampicillin as part of appendicitis or community-acquired pneumonia therapy, one can use either cefazolin or cefuroxime intravenously as a substitute in the interim

• Orally, one can use cefuroxime axetil. If meningitis coverage is needed, ceftriaxone can be safely used