D1.249 - Improving inpatient antimicrobial stewardship through single dose oral amoxicillin challenge among penicillin allergic veterans

Approximately 10% of the United States population reports having a beta-lactam allergy, although nearly 90% do not have true immunoglobulin E (lgE)-mediated reactions. This misconception results in the use of nonpreferred antibiotics, leading to antimicrobial resistance and treatment failure. We implemented a pharmacist-driven amoxicillin oral challenge program for penicillin allergic patients admitted to a Veterans Affairs hospital. The goal of this program was to remove inappropriate or outdated penicillin allergies. The purpose of this study was to evaluate the safety and efficacy of our penicillin allergy de-labelling.

Veteran inpatients were identified via chart review as candidates to receive a onetime dose of oral amoxicillin 500 mg based on criteria in Table 1. The Clinical Pharmacy Practitioner or Allergy/Immunology physician discussed the risks and benefits of the procedure and verbal consent was obtained. For low-risk penicillin allergies, the patient was administered a single dose of amoxicillin with an immediate 1-hour observation period and a follow-up 24 hours later for any delayed reaction.

From 05/25/2022 to 10/24/2024, 70 patients received an inpatient oral challenge with amoxicillin. None developed an acute or delayed allergic reaction. We also identified 8 patients with moderate risk penicillin allergies who were eligible for penicillin skin testing, performed by the Allergy and Immunology physician. Only 1 patient had a positive reaction during the skin test, with mild lip tingling. The remaining 7 skin tests were negative, and they received an amoxicillin oral drug challenge with no acute or delayed reaction, see Figure 1. Overall, 74/78 (95%) patients had their penicillin allergy label removed through the inpatient amoxicillin oral challenge process.

Amoxicillin oral challenge for inpatients with low-risk penicillin allergies was a successful strategy for penicillin allergy clearance in our Veteran population. While further investigation is needed to examine the long-term outcomes of penicillin allergy removal, our pharmacist-run and Allergy/Immunology physician supported penicillin de-labeling program targeting low-risk patients proved to be safe and effective for allergy removal.