Penicillin Allergy Delabeling in Syphilis Patients Assists in Furthering Treatment

BOSTON (Oct. 24, 2024) – About 10% of Americans believe they are allergic to penicillin, and approximately 90% of those patients are not actually allergic. As a result, those with the penicillin allergy label are often prescribed more toxic, dangerous and expensive antibiotics that might not be necessary or effective. A new study being presented at this year’s American College of Allergy, Asthma and Immunology (ACAAI) Annual Scientific Meeting in Boston showed that syphilis patients labeled as penicillin allergic who are low risk should be delabeled to avoid treatment failure and other negative health consequences.

“The number of people with untreated syphilis in the United States is at its highest since the 1950s, and penicillin is the preferred, most effective antibiotic for syphilis.” says allergist Cosby Stone, MD, MPH, senior author of the study and ACAAI member. “With the goal of delabeling patients with syphilis who believed themselves to be allergic to penicillin, we collected data on demographics, syphilis stage, results of penicillin allergy testing, use of second-line treatment, healthcare utilization and use of penicillin after delabeling, and clearance of syphilis. Importantly, among those who came to us for penicillin allergy testing, we noticed a pattern in which more than half had failed other treatments, doxycycline in particular, before penicillin allergy testing was even considered.”

Of the 12 patients identified, 12 out of 12 were ultimately delabeled of their penicillin allergy. Nine of 12 had documented subsequent penicillin treatment, while 3 of 12 had incomplete histories or lost follow up. Of the 9 who received penicillin, 5 had clearance, 3 had failed clearance (2  for reinfection, 1 for unknown reasons), and 1 had unknown clearance outcome. 

The authors conclude that most patients labeled as penicillin allergic should have their allergies evaluated as quickly as possible after a syphilis diagnosis and should be aggressively delabeled to avoid treatment failure, increased healthcare utilization, and negative public health consequences.

Abstract Title: A CALL TO ACTION FOR PENICILLIN ALLERGY DELABELING IN PATIENTS WITH SYPHILIS (Full abstract below)

Presenter: Aiwei Yan, MD 

For more information about drug allergies, or to find an allergist in your area, visit AllergyandAsthmaRelief.org. The ACAAI Annual Scientific Meeting is Nov. 9-13. For more news and research from the ACAAI Scientific Meeting, go to our newsroom and follow the conversation on X/Twitter #ACAAI24.

About ACAAI

The American College of Allergy, Asthma & Immunology (ACAAI) is a professional medical organization of more than 6,000 allergists-immunologists and allied health professionals, headquartered in Arlington Heights, Ill. Founded in 1942, the College fosters a culture of collaboration and congeniality in which its members work together and with others toward the common goals of patient care, education, advocacy, and research. ACAAI allergists are board-certified physicians trained to diagnose allergies and asthma, administer immunotherapy, and provide patients with the best treatment outcomes. For more information and to find relief, visit AllergyandAsthmaRelief.org. Join us on Facebook, Pinterest, Instagram and X/Twitter. 

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A CALL TO ACTION FOR PENICILLIN ALLERGY DELABELING IN PATIENTS WITH SYPHILIS 

1. Yan*1, G. Koo1, C. Allocco1, E. Phillips2, C. Stone1, 1. Nashville, TN; 2. Franklin, TN.

Introduction: The number of people with untreated syphilis in the United States is at its highest since the 1950s. Penicillin, the first-line treatment for syphilis, may be avoided in those labeled as penicillin allergic, thus fueling the public health crisis, risk of congenital syphilis, individual morbidity, and excessive healthcare utilization.

Methods: We retrospectively reviewed penicillin allergy labeled patients with confirmed syphilis referred to our drug allergy clinic for assessment and delabeling from January 2014 to January 2024. We collected data on demographics, syphilis stage, results of penicillin allergy testing, use of second-line treatment, healthcare utilization and use of penicillin after delabeling, and clearance of syphilis. 

Results: Of 12 patients identified, 83.3% were male and the median age was 39. Prior to our evaluation, 9 patients were treated with doxycycline, some multiple times (5 successful and 7 failed treatments total). One ceftriaxone-treated patient failed treatment. Three patients were desensitized to penicillin in the ICU. One female patient treated with penicillin desensitization had a pregnancy complicated by congenital syphilis. 12/12 patients were ultimately delabeled of their penicillin allergy. 9/12 had documented subsequent penicillin treatment, while 3/12 had incomplete/lost follow up in our EHR. Of the 9 who received penicillin, 5 had clearance, 3 had failed clearance (2 reinfection, 1 unknown reasons), and 1 had unknown clearance outcome. 

Conclusion: Syphilis is an individual and public health emergency. We have shown that most patients labeled as penicillin allergic that are low risk should be aggressively delabeled to avoid treatment failure, increased healthcare utilization, and negative public health consequences. 

Syphilis and Penicillin Allergy Testing Cases (n=12)