SELECTED ARTICLES FROM THE RECENT LITERATURE 2004
12/8/04
Is it safe to use carbapenems in penicillin allergic individuals?
Summary
Background - Allergic reactions to penicillin (PC) are generally directed against the beta-lactam component of the PC molecule. Allergy to PC is one of the most common drug allergies reported by patients. This history has major implications for the risk of using more recent agents in the beta-lactam group such as the carbapenems (Carb) (e.g. imipenam/cilastin). Carb agents are often not prescribed for those with "PC allergy" histories.
Findings - Sodhi et al of the Huron Hospital in East Cleveland, OH reviewed retrospectively the records of all individuals who received Carb agents over a 2 year period. Of the 163 of such patients who had given a previous history of PC allergy 15 (9.2%) developed hypersensitivity reactions during treatment with Carb agents. This compared with a 3.9% incidence of hypersensitivity reactions to Carb agents in those without a history of previous PC allergy. These two frequencies were not significantly different.
Conclusions - The true incidence of cross-allergenicity between PC and Carb agents may be lower than previously reported. Cautious administration of Carb agents may be appropriate in those with histories of PC allergy when needed.
Reference
J Antimicrob Chemother 2004;E pub. Editor's Comments
The question investigated in this study is very important, in light of the increasing use of Carb agents. However, I think that this study suffers from the same failing present in many retrospective reviews. Such studies depend on drug allergy histories gleaned from medical records without the patients being carefully questioned by someone very familiar with distinguishing likely true allergic reactions from other adverse events mis-interpreted as drug reactions. In the study described above, there is the peculiar finding that 163 of the 266 patients given Carb agents had histories of previous PC allergy reactions (61%). This is much higher than reported for the general frequency of PC allergy. One would question such histories of PC allergy: 1) likely many reported reactions occurred many years ago in childhood with the rash attributed to PC allergy actually an exanthem due to infection for which PC treatment was started; 2) even if the reaction years ago was due to PC allergy it is known that PC allergy can wane with time.
Thus, we would want to know what percentage of the "PC allergic"patients described above would have manifested a hypersensitivity reaction if treated with PC rather than Carb. Other studies suggest an incidence in adults of about 10%, about the same as the 9.2% incidence of Carb induced reactions reported in this study.
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