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Low- or no-risk penicillin allergy can be confirmed with oral challenge test

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Janet Christenbury

The Emory researchers say that 10 percent of hospitalized patients report a penicillin allergy, however recent studies show that approximately 98 percent of these patients are not acutely hypersensitive to the medication.

Many patients list a penicillin allergy on medical forms, but often these allergies are unconfirmed, or low-risk. Emory University researchers are trying to combat penicillin allergy labels in patients in these categories. They have determined direct oral amoxicillin (penicillin antibiotic) challenges in the doctor’s office, without prior skin testing, is acceptable in the unconfirmed or low-risk penicillin allergy population. Their findings were published recently in the journal, Allergy & Asthma Proceedings.

The Emory researchers explain that 10 percent of hospitalized patients report a penicillin allergy, however, recent studies indicate that approximately 98 percent of these patients are not acutely hypersensitive, or are tolerant of penicillin. In fact, according to the American Academy of Allergy, Asthma & Immunology, most people lose their penicillin allergy over time, even patients with a history of severe reaction such as anaphylaxis (a severe, potentially life-threatening allergic reaction). 

“Unconfirmed penicillin allergy has emerged as a public health issue, and an evaluation of penicillin allergy labels is recommended to improve antibiotic stewardship,” says Merin Kuruvilla, MD, assistant professor in the Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University School of Medicine, and first author on the published paper. “Penicillin is a very effective drug used to treat many different illnesses, yet many people avoid it because of their reported allergy. Our research should help patients determine if their penicillin allergy exists, and if not, they can remove it from their listed allergies in their health record.”

The most widely accepted protocol for testing for a penicillin allergy is penicillin skin testing, followed by oral amoxicillin challenge testing. Amoxicillin is a penicillin antibiotic used to treat bacterial infections. However, time constraints and resources may often preclude this process, according to the Emory authors. In individuals with low-risk penicillin allergy, recent research supports the safety and efficacy of a direct oral amoxicillin challenge.

The researchers retrospectively evaluated direct oral challenge acceptance and outcomes in eligible adult outpatients visiting an allergy clinic with a penicillin allergy label, over a six-month period. Direct oral amoxicillin challenge was recommended in patients with a history of benign rash, benign somatic symptoms (pain, fatigue), or unknown history associated with the last penicillin exposure greater than 12 months ago. Those with severe reactions or reactions within 12 months of evaluation were not challenged. The patients were monitored for 60 minutes after the challenge and were instructed to call the allergist’s office in the event of a delayed reaction.

Fifty of 355 adults (14 percent) seen by a single allergist had a penicillin allergy label. Of these patients, 38 (76 percent) met the criteria for a direct oral challenge. The index penicillin-associated reactions, for the most part, occurred greater than 10 years earlier. Reactions were predominantly reported as urticaria (hives), rash or an unknown reaction. Four patients (8 percent) were de-labeled based on history alone.

Twenty subjects (40 percent) consented to a challenge in the allergy clinic, and none developed immediate delayed hypersensitivity reactions, to the researchers’ knowledge. Three of the 20 patients (15 percent) developed self-limited subjective symptoms such as dizziness that were not deemed to constitute true immunoglobulin E-mediated hypersensitivity. At the end of the evaluation period, a total of 24 patients (48 percent) had the penicillin allergy label removed from their medical record.

“This study added to the accumulating body of evidence that supports the safety and efficacy of direct oral penicillin challenge without preliminary skin testing, which helps us to exclude penicillin allergy in individuals at low risk,” says Kuruvilla. “We are pleased with these findings in this small review of patients. We feel larger prospective studies are still needed to confirm these observations.”

Other Emory researchers in this study include: Jennifer Shih, MD; Kiran Patel, MD and Nicholas Scanlon, MD.


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