D1.391 - Pharmacist-led Risk-based β-Lactam Challenges in Patients with Penicillin Allergy: Impact on Antibiotic Days

Inaccurate penicillin allergy labels can lead to inappropriate antimicrobial use, increased adverse events, and higher healthcare costs. Structured, risk-based β-lactam challenges in low-risk patients have been shown to be safe and effective in facilitating appropriate antibiotic use without necessarily changing the allergy label¹. Pharmacist-led programmes incorporating risk stratification and drug challenges may facilitate appropriate β-lactam use in clinical practice.

We conducted a retrospective review of adult inpatients identified by a pharmacy-led antimicrobial stewardship program or infectious diseases consultation in a district hospital between 1 May 2024 and 30 November 2025 with a self-reported or documented penicillin allergy. Patients assessed as low risk (PEN-FAST² score <3) underwent graded, two-step inpatient challenges to cephalosporins with alternative R-group side chains or carbapenems, followed by 24-hour observation.

Eighty-four patients were reviewed. Allergy labels were recorded more than 10 years prior in 55 patients (65.5%), 33 (39.3%) had multiple drug allergy labels, and 14 (16.7%) had more than one penicillin-based antibiotic listed. Reaction details were unknown or unable to be recalled in 45 patients (53.6%), and 31 (36.9%) reported reactions occurring after the first dose. No patients had a history of severe cutaneous adverse drug reactions. Sixty-seven patients (79.8%) underwent an alternative β-lactam challenge. The most commonly challenged agent was ceftriaxone (47/67, 70.1%), with 4 patients (6.0%) challenged to a carbapenem. Immediate reactions occurred in 4 patients (6.0%) (urticaria, n=3; angioedema with shortness of breath, n=1), and delayed reactions in 2 patients (3.0%). Use of alternative β-lactam challenges was associated with a median reduction of 4 antibiotic days saved per patient.

A pharmacist-led antimicrobial stewardship approach incorporating risk-based alternative β-lactam challenges enabled safe β-lactam use in most patients with penicillin allergy labels and achieved a meaningful reduction in unnecessary antibiotic exposure. This strategy supports improved antimicrobial stewardship while maintaining patient safety.

References

1. Chua KYL, Vogrin S, Bury S, et al. The Penicillin Allergy Delabeling Program: A Multicenter Whole-of-Hospital Health Services Intervention and Comparative Effectiveness Study. Clin Infect Dis. 2021;73(3):487–496.
2. Trubiano JA, Vogrin S, Chua KYL, et al. Development and Validation of a Penicillin Allergy Clinical Decision Rule. JAMA Intern Med. 2020;180(5):745–752.