Β-lactam allergy

Cross-reactivity

	C-7 G1	C-7 G2	C-7 G3	C-3 G1	C-3 G2	C-3 G3	C-3 G4	C-3 G5	C-3 G6	C-3 G7
Penicillin	X
Ampicillin		X
Amoxicillin		X
Cefazolin
Cephalexin		X		X
Cefadroxil		X		X
Cephalothin	X					X
Cefotetan					X
Cefoxitin	X							X
Cefuroxime								X
Cefaclor		X
Cefotaxime			X			X
Ceftriaxone			X
Ceftazidime										X
Cefixime									X
Cefdinir
Cefipime			X
Ceftaroline

C-7 Side Chains

• Group 1: penicillin, cephalothin, cefoxitin
• Group 2: amoxicillin, ampicillin, cefaclor, cephalexin, cefadroxil
• Group 3: cefipime, cefotaxime, ceftriaxone

C-3 Side Chains

• Group 1: cefadroxil, cephalexin
• Group 2: cefotetan
• Group 3: cefotaxime, cephalothin
• Group 4
• Group 5: cefuroxime, cefoxitin
• Group 6: cefixime
• Group 7: ceftazidime

Comparison of R1 and R2 structural similarities between b-lactam drugs

Drugs that have identical R1 or R2 structures are listed as R1 (red cell) or R2 (gold cell). If only the ring or branch chain moiety of the R1 structure is identical, it is listed as R10 or R100, respectively. Drugs that have similar R1 or R2 structures are listed as r1 or r2. If only the ring or branch chain moiety of the R1 structure is similar, it is listed as r10 or r100, respectively. Blank cells imply no R1 or R2 structural similarities.

Hypersensitivity Reactions

• Type I (IgE-mediated)
  • Anaphylaxis
  • Itchy rash
  • Penicillins should be avoided
• Type II (IgG-mediated)
  • Non-itchy rash
  • Rash will improve if treatment continues, no need to avoid penicillins
• Type IV (cell-mediated)
  • Toxic epidermal necrolysis
  • Stevens-Johnson syndrome
  • Penicillins should be avoided

Further Reading

• Zagursky RJ and Pichichero ME.Cross-reactivity in β-Lactam Allergy. J Allergy Clin Immunol Pract. 2018;6(1):72-81.e1.