Can a patient with a penicillin allergy who has received intravenous (IV) Rocephin (ceftriaxone) take oral cefdinir?

Cefdinir Can Be Safely Administered to Patients with Penicillin Allergy Who Have Tolerated IV Ceftriaxone

Patients with penicillin allergy who have already received and tolerated intravenous ceftriaxone (Rocephin) can safely take oral cefdinir, as the risk of cross-reactivity is minimal (approximately 2.11%) for these third-generation cephalosporins with dissimilar side chains. 1

Understanding Cross-Reactivity Between Penicillins and Cephalosporins

• The traditional belief of 10% cross-reactivity between penicillins and cephalosporins is outdated and inaccurate 2

• Cross-reactivity varies significantly based on:

  • The generation of cephalosporin
  • Side chain similarity to penicillin
  • Type of allergic reaction (immediate vs. delayed)
  • Time since the allergic reaction occurred

• Cross-reactivity rates by cephalosporin type 1:

  • Aminocephalosporins (e.g., cephalexin, cefadroxil): 16.45%
  • Cephalosporins with intermediate similarity: 5.60%
  • Cephalosporins with dissimilar side chains (including ceftriaxone and cefdinir): 2.11%

Risk Assessment for This Specific Scenario

Low Risk Factors

• Patient has already received and tolerated IV ceftriaxone (Rocephin)
• Both ceftriaxone and cefdinir are third-generation cephalosporins with dissimilar side chains compared to penicillin
• Successful tolerance of one cephalosporin strongly predicts tolerance of other cephalosporins with similar side chains

Clinical Recommendations

1. The Dutch Working Party on Antibiotic Policy (SWAB) recommends that cephalosporins with dissimilar side chains can be used in patients with suspected immediate-type penicillin allergy, regardless of severity and time since the reaction 3

2. The FDA label for cefdinir only contraindicates its use in patients with known allergy to the cephalosporin class of antibiotics, not penicillin allergy 4

3. Since the patient has already received and tolerated IV ceftriaxone, this demonstrates that they do not have cross-reactivity with this particular cephalosporin structure

Practical Approach

• Proceed with oral cefdinir administration
• No special precautions are necessary since the patient has already demonstrated tolerance to a similar cephalosporin (ceftriaxone)
• Document the successful administration of both ceftriaxone and cefdinir to help guide future antibiotic selection

Important Caveats

• If the patient had experienced a severe delayed hypersensitivity reaction to penicillin (such as Stevens-Johnson Syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms), more caution would be warranted 5
• If this were a first-time cephalosporin exposure in a patient with penicillin allergy, monitoring for potential reactions would be recommended, particularly if the reaction to penicillin was severe and recent 1

Conclusion

The evidence strongly supports that a patient who has already tolerated IV ceftriaxone can safely take oral cefdinir, regardless of their penicillin allergy history. The successful administration of ceftriaxone effectively demonstrates the absence of cross-reactivity with this particular cephalosporin structure.