From the Guidelines
Ancef (Cefazolin) is not contraindicated with an Amoxicillin allergy.
Key Points
- The risk of cross-reactivity between Cefazolin and Amoxicillin is negligible due to their dissimilar side chains 1.
- Cefazolin has a unique side chain that does not share any similarity with the currently available penicillins, including Amoxicillin 1.
- The Dutch Working Party on Antibiotic Policy guideline recommends that patients with a suspected immediate-type allergy to penicillins can receive Cefazolin, irrespective of severity or time since the index reaction 1.
- A meta-analysis found that the risk of cross-reactivity to Cefazolin among patients with a proven penicillin allergy is less than 1% 1.
Important Considerations
- The risk of cross-reactivity may vary depending on the specific penicillin and cephalosporin involved, as well as the individual patient's allergy history 1.
- In cases of suspected severe or immediate-type allergy, it is recommended to use caution and consider alternative antibiotics or perform allergy testing 1.
- Cefazolin can be used in patients with a suspected non-severe, delayed-type penicillin allergy, but it is recommended to use caution and consider alternative antibiotics or perform allergy testing 1.
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 explicitly state that Ancef (Cefazolin) is contraindicated with an Amoxicillin allergy.
- Cephalosporin and Amoxicillin are different classes of antibiotics, although both are types of beta-lactam antibiotics. Since the label only mentions a contraindication for patients with a known allergy to the Cephalosporin group, not Penicillins (the class of antibiotics that includes Amoxicillin), no conclusion can be drawn about an Amoxicillin allergy specifically 2.
From the Research
Cefazolin and Penicillin Allergy
- Cefazolin, also known as Ancef, is a first-generation cephalosporin antibiotic often used in surgery to treat or prevent bacterial infection of the surgical site 3.
- The widely quoted cross-allergy risk of 10% between penicillin and cephalosporins is a myth, and cefazolin can be prescribed safely for penicillin-allergic patients 4.
Cross-Reactivity between Cefazolin and Penicillin
- Cefazolin use is safe and should be recommended for patients with a penicillin allergy, including those who experience Immunoglobulin E-mediated reactions such as anaphylaxis, unless they have a history of a severe, life-threatening delayed hypersensitivity reaction manifested as severe cutaneous adverse reactions (Steven-Johnson Syndrome), hepatitis, nephritis, serum sickness, and hemolytic anemia in response to penicillin administration 5.
- More than 90% of those with a documented penicillin allergy do not have true allergies on skin testing, and increased referral for penicillin allergy testing should be incorporated into routine care to reduce suboptimal antibiotic prophylaxis use 5.
Amoxicillin Allergy and Cefazolin
- Amoxicillin is the beta-lactam most often involved in immediate hypersensitivity reactions (IHRs), and cefadroxil is the most likely cephalosporin to cross-react with amoxicillin, since they share the same R1 side chain, unlike cefuroxime, with a structurally different R1 6.
- Cross-reactivity with cefazolin in amoxicillin allergic patients is not directly addressed in the provided studies, but the frequency of dual allergy to cefazolin and a natural penicillin is estimated to be 0.7% (95% credible interval [CrI], 0.1%-1.7%) 7.
Safety of Cefazolin in Penicillin-Allergic Patients
- Most patients with a penicillin allergy history may safely receive cefazolin, with the exception of patients with confirmed penicillin allergy, in whom additional care is warranted 7.
- The frequency of penicillin allergy was 4.4% (95% CrI, 0%-23.0%) for the studies that exclusively assessed surgical patients allergic to cefazolin 7.