Cephalosporin use in treatment of patients with penicillin allergies.

OBJECTIVE To review the evidence that supports the use of certain cephalosporins in penicillin-allergic patients. DATA SOURCES Published articles were identified through Medline and EMBASE (1960-2007) using the search terms penicillin and allergy and cephalosporin and cross-reactivity. Additional sources were identified from the authors' personal collection and the reference bibliographies. STUDY SELECTION The articles found in the search were limited to the English language and screened for relevance. Review articles and republication of results were excluded. A total of 44 articles reported evidence of cross-reactivity between cephalosporins and penicillins in human and animal studies. Additional references provided background and perspective. DATA SYNTHESIS Physicians may now prescribe certain cephalosporins in patients with a history of a nonserious, non-life-threatening penicillin reaction. Exclusions include type I anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis, angioedema, and other potentially life-threatening responses to medication. Recent reports demonstrate that a considerable body of literature describing the cross-reactivity between cephalosporins and penicillin was established based on nonallergic adverse reactions or in vitro studies rather than on clinically relevant immune-mediated reactions. Oral rechallenge and skin testing data support the relationship of the beta-lactam side-chain structures of these drugs as a predictor of cross-reactivity. CONCLUSION Recent data suggest that the incidence of cross-reactivity among penicillins and cephalosporins is lower than historically reported. Pharmacists should be aware that cephalosporin cross-reactivity in a penicillin-allergic patient is not necessarily a class effect. Dispensing should be evaluated based on the type of allergic manifestations and the drug prescribed.