Is there cross-reactivity between penicillins and cephalosporins?
BACKGROUND
We sought to determine the risk of an allergic reaction to a cephalosporin exposure in those with prior penicillin reactions.


METHODS
We conducted a retrospective cohort study using the United Kingdom General Practice Research Database. We selected all patients receiving a prescription for penicillin followed by a prescription for a cephalosporin and identified allergic-like events within 30 days after each prescription. Allergic events were defined by 2 sets of codes: 1 more restrictive, 1 more inclusive. Comparison was made with a population of patients receiving a prescription for a penicillin followed by a prescription for a sulfonamide antibiotic.


RESULTS
A total of 3,375,162 patients received a penicillin; 506,679 (15%) received a subsequent cephalosporin. Among patients receiving a penicillin followed by a cephalosporin, the unadjusted risk ratio of an allergic-like event for those who had a prior event, compared with those who had no such prior event, narrowly defined, was 10.1 (confidence interval 7.4-13.8). The absolute risk of anaphylaxis after a cephalosporin was less than 0.001%. The unadjusted risk ratio for sulfonamide antibiotic, rather than cephalosporin after penicillin allergic-like events was 7.2 (confidence interval 3.8-13.5).


CONCLUSIONS
Patients with allergic-like events after penicillin had a markedly increased risk of events after either subsequent cephalosporins or sulfonamide antibiotics. Cross-reactivity is not an adequate explanation for this increased risk, and the risk of anaphylaxis is very low. Thus, our data indicate that cephalosporins can be considered for patients with penicillin allergy.
Division of Pulmonary, Allergy Critical Care Medicine, Department of Medicine, Philadelphia, Pa, USA. apter@mail.med.upenn.edu
Andrea J
AJ
Apter
Judith L
JL
Kinman
Warren B
WB
Bilker
Maximilian
M
Herlim
David J
DJ
Margolis
Ebbing
E
Lautenbach
Sean
S
Hennessy
Brian L
BL
Strom
D000293:Adolescent; D000328:Adult; D000368:Aged; D000707:Anaphylaxis / Q000139:chemically induced; D000799:Angioedema / Q000139:chemically induced; D000900:Anti-Bacterial Agents / Q000276:immunology*; D002511:Cephalosporins / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003429:Cross Reactions; D003872:Dermatitis / Q000209:etiology; D004342:Drug Hypersensitivity / Q000209:etiology* / Q000276:immunology; D004892:Erythema Multiforme / Q000139:chemically induced; D005260:Female; D006801:Humans; D007223:Infant; D007826:Laryngismus / Q000139:chemically induced; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010406:Penicillins / Q000276:immunology*; D012189:Retrospective Studies; D013262:Stevens-Johnson Syndrome / Q000209:etiology; D014581:Urticaria / Q000139:chemically induced
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D010406:Penicillins