Allergic to penicillin? Review calls for deeper probe

A paper today in the Journal of the American Medical Association recommends evaluation of reported penicillin allergy as an important tool for antimicrobial stewardship.

An estimated 10% of the US population, some 32 million people, have a documented penicillin allergy. In many cases, patients receive the label as children, as penicillin and other beta-lactam antibiotics are frequently prescribed for common pediatric infections. Hives, benign rashes, and gastrointestinal issues are among the most commonly reported reactions.

Yet studies have shown that more than 95% of patients reporting penicillin allergy are not truly allergic to this class of antibiotics, and the incidence of serious anaphylactic reactions is extremely low. Furthermore, in roughly 80% of patients who've had an anaphylactic reaction, the allergy wanes after 10 years.

Consequences of mislabeling

When people are labeled as having a penicillin allergy, the clinical consequences can be significant. For one, patients with infections that would typically be treated with penicillin or other beta-lactam drugs instead receive antibiotics that aren't as effective and may be more expensive. Additionally, treatment with broader-spectrum agents can increase the risk of Clostridium difficile and other adverse reactions.

In today's review, commissioned by the American Academy of Allergy, Asthma, and Immunology, the Infectious Diseases Society of America, and the Society for Healthcare Epidemiology of America, researchers from Massachusetts General Hospital (MGH), Kaiser Permanente, and Northwestern Medicine say these consequences—and the potential to reduce antimicrobial resistance by replacing broad-spectrum antibiotics with narrow-spectrum agents—underscore the importance of confirming documented penicillin allergies in all patients.

"Evaluation of penicillin allergy has substantial benefits for patients by allowing improved antimicrobial choice for treatment and prophylaxis," the authors write. "As a component of antimicrobial stewardship efforts, evaluation of penicillin allergy leads to more appropriate antibiotic administration and may reduce antimicrobial resistance and cases of C difficile infection."

Determining who has a true allergy

The review recommends that clinicians begin by performing a comprehensive allergy history to assess reported reactions and determine the level of risk that patients have for a true penicillin allergy.

Patients who've reported isolated, non-allergic reactions to penicillin—like stomach upset, headache, or itchy skin with no rash, for example—would be considered low-risk, while patients who've experienced hives or shortness of breath, but haven't had anaphylactic reactions, would be in the moderate-risk category. The high-risk category is for patients who've had documented anaphylactic reactions to penicillin.

Those categories, in turn, inform how clinicians should proceed. For the low-risk patients, the review recommends either prescribing a course of amoxicillin or performing a direct amoxicillin challenge, in which patients are given a dose of the drug and then observed for a period. Moderate-risk patients should receive a penicillin skin test first, followed by a direct amoxicillin challenge if the test is negative. Patients with a history of high-risk reactions should be referred to a specialist.

The review also recommends that, when skin testing is negative and direct amoxicillin challenges are tolerated, patient medical records should be updated and patients educated so that they understand they don't have a penicillin allergy.

The review's corresponding author, Erica Shenoy, MD, PhD, of the MGH division of infectious diseases, says the evaluation of documented penicillin allergy can benefit patients in all medical settings in which beta-lactams are commonly used, from pediatrics to oncology to long-term care.

"If I had my way, verification of a penicillin allergy would be on many of our checklists, just like age-related screenings and immunizations," Shenoy said in an MGH press release. "Evaluating a reported penicillin allergy, regardless of the current need for an antibiotic, can lead to really important benefits for our patients."

See also:

Jan 15 JAMA abstract

Jan 15 MGH press release

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