Side chains shared by aminopenicillins and aminocephalosporins

Some penicillins and cephalosporins share identical or similar side chain groups, leading to possible clinical cross-reactivity. Ampicillin has the same side chain in the R1 position as cephalexin and cefaclor, as well as cephradine, cephaloglycin, and loracarbef (not shown). Amoxicillin has the same side chain as cefadroxil, cefatrizine, and cefprozil (not shown).