Which class of antibiotics should be avoided in patients with a known allergy to penicillin?

Cephalosporins should be avoided in patients with a known allergy to penicillin due to the structural similarities between the two classes of antibiotics. Both penicillins and cephalosporins contain a beta-lactam ring, which is the common feature responsible for their antimicrobial activity and associated allergic reactions. Consequently, patients who are allergic to penicillin may also react similarly to cephalosporins, which can lead to severe allergic reactions, including anaphylaxis.

While other classes of antibiotics, such as macrolides, aminoglycosides, and tetracyclines, are generally considered safe for use in individuals with a penicillin allergy, cephalosporins pose a higher risk due to potential cross-reactivity. Therefore, prescribing cephalosporins should be approached with caution or avoided altogether in such patients. Understanding these relationships helps clinicians make safer prescribing decisions and provide optimal patient care.