Penicillin and cephalosporins share a common beta-lactam structure. People who are allergic to penicillin are approximately 4 times more likely to develop an allergic reaction to a cephalosporin than those people who have no penicillin allergy (from 5–16% of patients allergic to penicillin develop reactions to cephalosporins).

See also separate profile for Ceftazidime & Avibactam.