Penicillin-allergic patients: Use of cephalosporins, carbapenems, and monobactams

Antigenic components of penicillins — In order to understand the possible cross reactivity among penicillins, cephalosporins, carbapenems and monobactams, it is helpful to review the potential allergens in penicillins. Patients with IgE-mediated allergy to penicillins may be reactive to the beta-lactam ring structure that is common to all penicillins, or to the R-group side chains that distinguish different penicillins from one another. In the United States, most penicillin allergic patients are sensitive to the beta-lactam core. In contrast, in southern Europe where amoxicillin constitutes 90 percent of antibiotic use in some countries, up to one third of patients are said to react to the R group side chain. (See "Allergy to penicillins".)