Penicillin Allergy: A Mountain or a Molehill?

Laurie Scudder, DNP, NP; Eric Macy, MD; Ramzy H. Rimawi, MD; Roland Solensky, MD


April 30, 2014

Editor's Note:
Penicillin "allergy" history is self-reported by about 1 out of 10 persons. Of 30 million US patients thought to be penicillin-allergic, an estimated 28.5 million actually are not, meaning that up to 19 of 20 patients who think they are allergic to penicillin are misinformed. A new study illustrates that this inaccurate history and subsequent avoidance of drugs in this class are linked to longer hospital stay, significantly more antibiotic use, and increased prevalence of Clostridium difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) infections.[1] Medscape spoke with Eric Macy, MD, from the Southern California Kaiser Permanente Medical Group, Department of Allergy, San Diego Medical Center, and lead author of this new research, about the clinical implications. Dr. Macy was joined by Ramzy H. Rimawi, MD, a fellow in the Department of Pulmonary and Critical Care Medicine at the Brody School of Medicine in Greenville, North Carolina, and Roland Solensky, MD, an allergist with the Corvallis Clinic in Corvallis, Oregon.

Medscape: Why is this issue of overreported penicillin allergy so important?

Dr. Rimawi: The Centers for Disease Control and Prevention (CDC) recently released Threat Report 2013, a snapshot of the burden and threats posed by antibiotic resistance, concluding that over 2 million infections and 23,000 deaths annually are the result of infections with antibiotic-resistant bacteria and fungi.[2] Following this release, the Strategies to Address Antimicrobial Resistance (STAAR) Act, supported by the CDC and other major healthcare professional organizations, was reintroduced in Congress. Antibiotic options are becoming limited by these drug-resistant pathogens, whether due to previous use of antibiotics or simply exposure to someone with a resistant infection. Antibiotic options are even more limited when patients report an allergy to antibiotics, most commonly penicillin, with an incidence at times as high as 20% of patients admitted to the hospital. Thanks to penicillin skin testing, numerous studies have shown that this incidence is largely inaccurate. In fact, 9 out of 10 patients who report penicillin allergy are proven to be tolerant when assessed by penicillin skin testing. There are 30 million people who report a penicillin allergy in the United States; thus, 27 million of these people are likely not allergic.[3] Whether a patient claims to be allergic because of a true or vague allergy in the past, clinicians must encourage patients to undergo penicillin skin testing in order to expand their antibiotic options, should that individual ever acquire a drug-resistant infection and need penicillin or a penicillin-like antibiotic.

Penicillin and penicillin-like antibiotics are still perhaps the most effective, cheapest, least toxic, and most widely used antibiotics. Penicillin skin testing will not only expand antibiotic options but may also allow providers to prescribe cheaper, more directed, less toxic antibiotics with little fear of precipitating an allergic reaction. In this era, when new antibiotics are not in the horizon, the use of antibiotics that were previously restricted by reported allergies may be a cornerstone in the battle against antibiotic resistance and rising healthcare costs.

Medscape: Dr. Macy, your very large study included over 50,000 hospitalized patients with a history of penicillin allergy and noted that that history was present in about 11% of all hospitalized patients. Can you speak to this figure?

Dr. Macy: Hospitalized patients tend to be older and sicker and are exposed to more antibiotics. Thus, we see a higher rate of penicillin "allergy" in hospitalized patients.

Medscape: Is 11% about the same percentage of self-reported penicillin allergy in the overall population?

Dr. Macy: In our entire health plan, the rate is only about 8%. This was a study of hospitalized patients, who have a higher rate of penicillin "allergy" than average health plan patients.

Medscape: Are there specific groups of patients that are most likely to self-report penicillin allergy?

Dr. Macy: Penicillin "allergy" accumulates over time. Thus, the rates are higher with increasing age.

Dr. Solensky: Patients who seek medical care more often and therefore end up being treated with antibiotics more frequently are more likely to have a reaction and end up with a label of penicillin allergy.


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