RT Book, Section A1 Gruenberg, Katherine A1 Guglielmo, B. Joseph A2 Papadakis, Maxine A. A2 McPhee, Stephen J. A2 Rabow, Michael W. A2 McQuaid, Kenneth R. SR Print(0) ID 1193121979 T1 Cephalosporins T2 Current Medical Diagnosis & Treatment 2023 YR 2023 FD 2023 PB McGraw-Hill Education PP New York, NY SN 9781264687343 LK accessmedicine.mhmedical.com/content.aspx?aid=1193121979 RD 2024/03/28 AB The cephalosporins, structurally related to the penicillins, consist of a beta-lactam ring attached to a dihydrothiazoline ring. Substitutions of chemical groups result in varying pharmacologic properties and antimicrobial activities. Type 1 allergic cross-reactions between penicillins and cephalosporins are primarily due to similarities in the molecular structure of the R side chains; for example, penicillin and cefoxitin have similar R side chains; ampicillin and cephalexin share similar side chains. Consequently, a patient with a type 1 reaction to penicillin would be more likely to experience a similar reaction with cefoxitin when compared with cephalexin. In contrast, a patient with an allergic reaction to ampicillin would be more likely to have a reaction to cephalexin than cefoxitin.