Low-risk cefalexin allergies are associated with inpatient prescribing of second-line non-beta-lactam antibiotics

Background: Cefalexin is a commonly prescribed oral antibiotic, with a similar side chain to amoxicillin. The objectives of this study were to (1) describe the frequency and nature of previously recorded cefalexin adverse reaction (AR) labels in the electronic medical record (EMR) in a medical inpatient cohort, (2) evaluate the accuracy of these labels and (3) examine the association between a cefalexin allergy label and the antibiotics prescribed during an inpatient admission. 

Methods: Consecutive admissions under general medicine in a tertiary hospital over a 1-year period were included in this retrospective cohort study. Data regarding cefalexin adverse reaction (AR) history, and antibiotics prescribed during admission were collected from the EMR. Cefalexin allergy descriptions were reviewed using expert criteria to determine whether the described reaction was most consistent with allergy or intolerance. 

Results: The number of admissions included in this study was 12,134. Of the 224 (1.9%) admissions with a recorded cefalexin AR, 196 (87.5%) had a label of allergy and 28 (12.5%) of intolerance. Following the application of expert criteria, 43 (21.9%) of cefalexin allergy labels were found to be consistent with intolerance. The presence of a low-risk cefalexin allergy was associated with an increased likelihood of receiving non-penicillin antibiotics including clindamycin and ciprofloxacin. 

Conclusion: Cefalexin AR are common, and frequently incorrectly classified in the electronic medical record with consequences for in-hospital antibiotic prescribing and antimicrobial stewardship.