What is the best antibiotic for burns in a patient allergic to Keflex (Cephalexin)?

Best Antibiotics for Burns in Patients with Cephalexin Allergy

For patients with burns who are allergic to cephalexin (Keflex), clindamycin is the recommended first-line antibiotic therapy due to its excellent coverage against common burn pathogens and safety in patients with cephalosporin allergies. 1

Antibiotic Selection Algorithm

First-line options:

• Clindamycin: 300-450 mg orally four times daily for adults or 20 mg/kg/day in 3 divided doses for children 1
  • Provides excellent coverage against Staphylococcus aureus (including MSSA) and Streptococcus species
  • Safe in patients with cephalosporin allergies
  • Note: Monitor for potential cross-resistance in erythromycin-resistant strains 1

Alternative options based on severity:

• For mild to moderate burns:

  • Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily for adults 1
    • Bactericidal activity against many common skin pathogens
    • No cross-reactivity with cephalosporins 1

• For moderate to severe burns:

  • Linezolid: 600 mg orally twice daily for adults 1
    • No cross-reactivity with beta-lactams
    • Effective against MRSA and other resistant gram-positive organisms
    • More expensive option 1

• For severe burns requiring IV therapy:

  • Vancomycin: 30 mg/kg/day in 2 divided doses IV for adults 1
    • Parenteral drug of choice for serious infections in penicillin/cephalosporin allergic patients
    • Effective against MRSA 1

Important Considerations for Cephalexin Allergy

• The nature of the cephalexin allergy is important to determine:

  • Immediate-type (IgE-mediated) reactions: Avoid other cephalosporins with similar side chains 1
  • Non-severe delayed-type reactions: May consider cephalosporins with dissimilar side chains 1

• Cross-reactivity between cephalosporins is primarily based on R1 side chains, not the beta-lactam ring itself 1

  • Cephalexin shares identical R1 side chains with amoxicillin 1
  • Avoid amoxicillin/clavulanate in patients with cephalexin allergy due to potential cross-reactivity 1, 2

• For patients with severe immediate-type reactions to cephalexin:

  • Avoid all beta-lactam antibiotics including penicillins 1
  • Clindamycin is the safest alternative 1

Special Considerations for Burns

• Burns are prone to polymicrobial infections requiring broad-spectrum coverage 1, 3
• Local wound cultures should guide therapy when available 3
• Consider topical antimicrobial agents in addition to systemic therapy for limited burn areas:
  • Mupirocin ointment: Apply to lesions twice daily 1
  • Retapamulin ointment: Apply to lesions twice daily 1

Common Pitfalls to Avoid

• Myth of 10% cross-reactivity: The widely quoted 10% cross-allergy risk between penicillins and cephalosporins is exaggerated. Actual cross-reactivity is much lower, approximately 1% 4, 2
• Overlooking side chain similarity: Cross-reactivity is primarily determined by R1 side chain similarity, not the beta-lactam ring 1
• Avoiding all beta-lactams unnecessarily: Third and fourth-generation cephalosporins with dissimilar side chains may be safe in patients with non-severe reactions to cephalexin 1, 2
• Inadequate coverage: Burns often involve polymicrobial infections, so ensure the selected antibiotic provides appropriate coverage 3