• Allergy to all beta-lactams is highly unlikely.
• Cross reactivity between beta lactam groups has been overstated in the past. It is more likely to be driven by side-chain similarity than allergy to the beta lactam ring itself.
• If a patient is truly allergic to penicillins, or the allergy cannot be challenged/successfully removed, recommended use of other beta lactams is below:

 

Cross-reactivity between beta lactams

Further information on side-chain similarity between different beta-lactam antimicrobials can be found in the table below. Important cross-reactions include:

• Penicillins and Cefalexin
• 3^rd generation cephalosporins with each other (e.g. ceftriaxone & ceftazidime)
• Aztreonam, ceftazidime & cefiderocol
• Carbapenems with each other (e.g. Meropenem and Ertapenem)

Modified from the Dutch Working Party on Antibiotic Policy 2023 Guidelines