From the Guidelines
Cephalexin allergy does not significantly cross-react with cefazolin, as cefazolin has a unique side chain that is dissimilar to cephalexin.
Key Points
- The risk of cross-reactivity between cephalosporins is dependent on the similarity of their R1 side chains 1, 2, 3.
- Cefazolin has a unique side chain and appears to have very low cross-reactivity with penicillins and other cephalosporins, including cephalexin 2, 4, 3, 5.
- Studies have shown that the risk of cross-reactivity between cefazolin and penicillins is negligible, with a reaction rate of 0.7% to 0.8% among patients with a confirmed penicillin allergy 2, 4.
- The Dutch Working Party on Antibiotic Policy guideline recommends that patients with a suspected immediate-type allergy to penicillins can receive cefazolin, as it does not share any side chains with currently available penicillins 5.
Cephalosporin Allergy and Cross-Reactivity
- Cephalosporin allergy is often dependent on the similarity of the R1 side chain to other cephalosporins or penicillins 1, 2, 3.
- Cephalexin, cefadroxil, cefprozil, and cefaclor are examples of cephalosporins that share similar side chains and may have a higher risk of cross-reactivity 1, 2.
- Cefazolin, on the other hand, has a unique side chain and is less likely to cross-react with other cephalosporins or penicillins 2, 4, 3, 5.
From the FDA Drug Label
CEFAZOLIN IS CONTRAINDICATED IN PATIENTS WITH KNOWN ALLERGY TO THE CEPHALOSPORIN GROUP OF ANTIBIOTICS. The FDA drug label does not provide specific information about cross-reactivity between cephalexin and cefazolin.
- Allergy to one cephalosporin may not necessarily predict allergy to another, but the label does not provide direct information to answer the question 6.
From the Research
Cephalosporin Allergy Cross-Reactivity
- Cephalosporins are a class of antibiotics that are commonly prescribed due to their wide clinical utility and general tolerability 7.
- The cross-reactivity potential of cephalosporins is related to the structural R1 side chain, and clinicians should be aware of R1 side chain similarities when prescribing alternate β-lactams in allergic individuals 7.
- There is a low likelihood of true cephalosporin allergy, and clinicians should consider this when clinically indicated 7.
Cefazolin and Penicillin Allergy
- Cefazolin is a first-generation cephalosporin antibiotic that is often used in surgery to treat or prevent bacterial infection of the surgical site 8.
- The incidence of cefazolin allergy has increased worldwide over the years, and the sensitization mechanism is currently unknown 9.
- Data supporting cross-reactivity between penicillins and cephalosporins are lacking, but studies suggest that previous exposure to cefazolin or structurally related chemical agents may contribute to sensitization 9.
Cross-Reactivity between Cephalosporins and Penicillins
- There exists cross-reactivity between cephalosporins and penicillins, and patients allergic to several penicillins are more likely to develop allergic reactions to cephalosporins 10.
- The cross-reactivity is due to sensitization to similar structural characteristics, including the nuclear structure and R1 side-chain 10.
- Penicillin-allergic patients may develop cross-allergic reactions with not only first-generation but also third-generation cephalosporins 10.
Cephalexin and Cefazolin Cross-Reactivity
- Cephalexin is a first-generation cephalosporin antibiotic that has a similar R1 side chain to cefazolin 7, 10.
- Studies suggest that there may be cross-reactivity between cephalexin and cefazolin due to their similar structural characteristics 10.
- However, the exact cross-reactivity potential between cephalexin and cefazolin is not well established and requires further study 7, 10.