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Beta-Lactams: Do They Deserve a Second Look?

Is it time to reassess prescribing practices on beta-lactams when it comes to patients with penicillin allergies? The answer is an unquestionable, “Yes!” according to Meghan Jeffres, PharmD, Assistant Professor in the Department of Clinical Pharmacy at the University of Colorado, Skaggs School of Pharmacy and Pharmaceutical Sciences, in Aurora, CO.
Dr. Jeffres spoke about the issues penicillin allergies present to practitioners, at the recent Society of Infectious Disease Pharmacists (SIDP) Society Day at the ASM Microbe 2017 conference on June 1, 2017, particularly considering the recent introduction of the PRE-PEN, a test for a penicillin allergy being used at many hospitals across the country.
According to Dr. Jeffres, the majority of penicillin allergy labels indicated for patients are inaccurate, and it is this inaccuracy that leads to an increase in the use of secondary antibiotics (such as vancomycin and fluoroquinolones). This increased use is potentially leading to an increase in resistant infections. In addition, further data has shown that the mislabeling of penicillin allergies has led to an increase in treatment failures and an overall cost increase to the patient.1,2,3,4  
Ask any practitioner, though, and once a patient is labeled as having a penicillin allergy, it’s hard to “declassify” them. When a prescriber goes to prescribe a preferred antibiotic to that patient, red flags abound in the electronic medical record on potential cross-reactivity for that antibiotic class for the patient. Dr. Jeffres argues, however, that we should not be looking at cross-reactivity among drug classes, but rather, between specific antibiotics, even within class.
For example, new research has shown that patients with a true-penicillin allergy tend to have similar reactions to those antibiotics that share a similar side chain with penicillin. To illustrate, Dr. Jeffres shared a chart (see Figure) with the audience showing the side chain similarities between cephalosporins and penicillin. She highlighted that cefoxitin and penicillin share a similar side chain, but cefazolin, for example, does not share a side chain with any beta-lactam.
Figure: Side Chain Similarities Between Cephalosporins and Penicillin1,2

1. Antunez et al. J Allergy Clin Immunol 2006;117:404-10.
2. DePestel et al. J Am Pharm Assoc. 2008;48(4):530-40.

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