Cephalosporin appears safe in patients with verified penicillin allergy
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Key takeaways:
- 49 of 50 patients with penicillin allergy tolerated 76 of 77 doses of cephalosporins.
- 70% of reactions were low risk, including isolated rashes and unknown reactions.
- Six patients had anaphylaxis.
High-risk patients with a verified penicillin allergy safely received cephalosporins, according to a letter published in The Journal of Allergy and Clinical Immunology: In Practice.
These findings may encourage changes in cephalosporin prescribing patterns, Ami P. Belmont, MD, clinical fellow in the section of rheumatology, allergy and immunology of thedepartment of internal medicine at Yale University School of Medicine, and colleagues wrote.
The study comprised 50 patients (median age, 51 years; 78% female) with verified penicillin allergy who received 77 unique cephalosporin courses or drug challenges in the Yale-New Haven Hospital Health System between 2014 and 2022.
Atopic histories appeared prevalent among these patients, with 38 (76%) meeting the criteria for multiple drug allergy labels and 19 known reactions (38%) to aminopenicillins among the index reactions. Overall, 15 patients had high-risk penicillin allergy histories and 35 had low-risk histories.
Also, the researchers classified 35 of the reactions (70%) as low risk, which included 28 cases of isolated rash, four cases of angioedema and six unknown reactions overall. There were six cases of anaphylaxis as well, with four patients who required epinephrine.
During skin testing, 19 patients (38%) were positive for ampicillin, 17 (34%) were positive for penicilloyl-polylysine and 16 (37%) were positive for penicillin-G. Also, seven (14%) were selectively positive for ampicillin and 14 (28%) demonstrated positive drug challenges.
One patient representing 2% of the full cohort and 1% of those who received cephalosporin had a reaction to cephalosporin. This patient’s history included asthma, chronic urticaria and eight drug allergy labels.
This patient experienced a pruritic erythematous rash within an hour of receiving the full dose during the amoxicillin drug challenge, with responses to antihistamine and prednisone. During a cephalexin drug challenge a month later, the patient developed an urticarial rash immediately, but this rash responded to antihistamines as well.
The other 49 patients (98%) tolerated 76 cephalosporin administrations, including 52 administrations with dissimilar side chains (68%) and 25 with similar side chains (32%).
The patients stratified by low risk and high risk received comparable proportions of cephalosporins with similar side chains, the researchers wrote, with no patients receiving cephalosporins with identical side chains. Also, 21 of the 22 patients (95.5%) who received aminocephalosporins did not have any reactions.
Expanded use of cephalosporins would probably reduce the higher risks for adverse outcomes that patients with penicillin allergy face, the researchers wrote, adding that cephalosporins are generally safe to administer even among patients with verified penicillin allergy, based on these findings.
The researchers also called for future studies that would evaluate whether these findings would extend to patients with verified penicillin allergy who have experienced recent or severe reactions.
Still, the researchers noted these findings will further promote changes in cephalosporin prescribing patterns in agreement with recently updated parameters for drug allergy practice.
Perspective
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Allison C. Ramsey, MD
These findings are not surprising, and they are certainly in line with my experience. The evidence has really evolved to indicate that the vast majority of patients with penicillin allergy can tolerate cephalosporins. Also, these findings are helpful in that they would allow for a whole class of antibiotics to be used when penicillins must be avoided. Cephalosporins are an important class of antibiotics that should not be unnecessarily avoided. Of course, bigger studies are always helpful, but I think it is encouraging that the field is moving this way.
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