Antimicrobial selection in the penicillin-allergic patient.

Patients frequently state that they have a penicillin allergy that often presents a therapeutic problem in treating a variety of infectious disorders. Penicillin and beta-lactam allergic reactions should be determined by a careful history. Many patients who say they have a penicillin allergy, in fact do not. If it is determined that the patient has a penicillin allergy, then the clinician should determine whether it is of an anaphylactic or nonanaphylactic variety. Most reactions to beta-lactams are of the nonanaphylactic variety and are usually manifested clinically as a mild maculopapular rash or drug fever. Uncommonly, penicillin allergies are clinically manifested as anaphylactic reactions, e.g., bronchospasm, laryngospasm, hypotension or hives. Patients' hypersensitivity reactions tend to be stereotyped on rechallenge, which make the reactions predictable. Patients who have a questionable penicillin allergy, or have had only fever or rash, may be safely given beta-lactam antibiotics without fear of anaphylaxis. Patients with a documented history of anaphylactic reactions should receive non-beta-lactam antibiotics. Although monobactams and carbapenems are structurally related to beta-lactams, they are unrelated in terms of allergic potential. There is no cross-reactivity between mono-bactams or carbapenems with beta-lactams, and these drugs may be used safely in patients with anaphylactic reactions to beta-lactams. Because so many antibiotics are available that are allergically unrelated to beta-lactams, beta-lactam desensitization procedures are rarely necessary. (c) 2001 Prous Science. All rights reserved.