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Penicillin Allergy Cephalosporin Cross-Reactivity — FRCA Final MCQ

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HardPreoperative AssessmentPenicillin Allergy Cephalosporin Cross-ReactivityFRCA Final

A 48-year-old woman (ASA II, 70 kg) with a known allergy to penicillin (anaphylaxis with documented IgE positivity) requires prophylactic antibiotics for a hip replacement. The standard prophylaxis is IV cefuroxime. Is cefuroxime safe in this patient?

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Correct answer: A — Cefuroxime is safe but only if given intramuscularly

The cross-reactivity between penicillins and cephalosporins has been historically overestimated. Current evidence suggests: first-generation cephalosporins have ~1-2% cross-reactivity with penicillins; second-generation (cefuroxime) has ~1% risk; third and fourth-generation have <0.5% risk. In patients with confirmed severe (IgE-mediated/anaphylactic) penicillin allergy, cephalosporins can be used with caution IF the specific side chains are different. However, many guidelines recommend avoiding cephalosporins and using alternatives (teicoplanin, vancomycin, clindamycin) in confirmed severe penicillin allergy. A perioperative allergy assessment is recommended.

Reference: NICE – 2020 – Drug allergy; BOA/BSAC – 2022 – Surgical antibiotic prophylaxis; RCOA – 2023 – Allergy module