Allergic Cross-Sensitivity Between Penicillin, Carbapenem, and Monobactam Antibiotics: What Are the Chances?

OBJECTIVE: To evaluate the literature on the allergic cross-reactivity between penicillin, carbapenem, and monobactam antibiotics. DATA SOURCES: A MEDLINE search (1950-June 2008) of the English literature was performed using the search terms P-lactam, penicillin, monobactam, carbapenem, allergy, and cross-reactivity. References of review articles were also screened for inclusion. STUDY SELECTION AND DATA EXTRACTION: All articles in English from the data source were identified. Studies whose primary goal was to evaluate drug hypersensitivity and the potential for cross-reactivity were evaluated. DATA SYNTHESIS: Many patients have reported penicillin allergies that have not been verified by skin testing; many healthcare providers avoid the use of other beta-lactam antibiotics, namely carbapenems, in these patients due to fear of the potential for immunoglobulin E-mediated allergic cross-reactivity. A wide range of cross-reactivity between penicillins and carbapenems has been reported in various studies; however, more recent prospective studies have shown the incidence of cross-reactivity between penicillin and carbapenern skin tests to be around 1%. Additionally, many prescribers freely use the monobactam aztreonam in penicillin-allergic patients, believing there is no cross-reactivity between the 2 drugs. Although data support the lack of cross-reactivity between aztreonam and penicillins, immunology and some clinical data support an interaction between ceftazidime and aztreonam due to the similarity of their side chains. CONCLUSIONS: Although variability in cross-reactivity rates between P-lactam classes exists in the literature, the practice of avoiding carbapenems in penicillin-allergic patients should be reconsidered. With regard to monobactams, the administration of aztreonam in a patient with a ceftazidime allergy may carry an increased risk of type 1 hypersensitivity reactions and should be considered with caution. Additionally, the importance of obtaining a thorough patient history regarding the previous allergic event, proper documentation, and penicillin skin testing is reemphasized.