The incidence of antimicrobial allergies in hospitalized patients - Implications regarding prescribing patterns and emerging bacterial resistance

Background: The development of antimicrobial guidelines is one way in which institutions attempt to control emerging resistance, but the real challeng e falls on promoting and ensuring adherence to these guidelines. Investigat ing reasons for the prescribing of alternative antimicrobial agents outside of these guidelines is crucial for modifying practices that may adversely impact institutional antimicrobial goals. Methods: Retrospective cross-referencing of computerized pharmacy printouts and concurrent manual medical record review. Results: Approximately 25% (470/1893) of the patients requiring antimicrobi al therapy reported an allergy to at least 1 antimicrobial agent. The most commonly reported antimicrobial allergy was penicillin (295/1893 [15.6%]). Eighty-five patients (18.1%) reported having an allergy to 2 or more antimi crobial agents. Only 4% (27/601) of the reported antimicrobial allergies co ntained documentation as to the nature of the specific allergic reactions, while a manual medical record review revealed that 32% (23/73) of the antim icrobial allergies contained documentation of the specific allergic reactio n. Ninety-eight (39.7%) of 247 patients reporting an allergy only to penici llin and/or cephalosporin received vancomycin in comparison with 247 (17.4% ) of 1423 patients without any antimicrobial allergies (P<.001). Similarly, 53 (21.5%) of 247 patients with reported penicillin and/or cephalosporin a llergies received levofloxacin compared with 114 (8.0%) of 1423 patients wi thout any antimicrobial allergy (P<.001). Conclusion: The incidence of penicillin allergy at our institution exceeds population averages. This finding, in combination with limited documentatio n of drug allergies, appears to lead to the prescribing of alternative anti microbial agents that do not fit into institutional antimicrobial guideline s and, in some instances, may put the patient at risk for infection and/or colonization with resistant organisms. Use of these alternative agents may adversely impact the ability to manage emerging antimicrobial resistance.