Cephalosporins Overview

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Summary

Cephalosporins are a class of antibiotics ‘used to treat a variety of bacterial infections. Like penicillins, these drugs are beta-lactam antibiotics; they are D-Ala-D-Ala analogs that bind to and block the bacterial transpeptidase, thereby preventing the cross-linking of the bacterial cell wall. Cephalosporins are also resistant to penicillinase, a bacterial enzyme that can deactivate penicillins by cleaving the beta-lactam ring. Because of this, many cephalosporins can be used to treat penicillin-resistant bacteria. However, cephalosporins also have a host of their own side effects. Firstly, patients may develop an allergic reaction after taking cephalosporins, which usually manifests as a rash. Taking cephalosporins can also lead to creation of auto-antibodies that cause hemolytic anemia. Finally, a disulfiram-like reaction to alcohol and vitamin K deficiency are important side effects seen with taking cephalosporins. 

Key Points

  • Cephalosporins
    • Mechanism
      • Beta-lactam antibiotics
        • Works in a similar fashion to penicillin to bind to penicillin-binding proteins (transpeptidases) and prevent cell wall cross-linking
          • In penicillins, beta-lactam is bonded to a penam (thiazolidine) ring, and a side chain
          • In cephalosporins, beta-lactam is bonded to a cepham dihydrothiazine ring
      • Bactericidal
    • Clinical Use
      • Different bacterial coverage dependent on generation of drug
    • Adverse Effects
      • Hypersensitivity (allergy)
        • Most commonly seen with cefazolin administered pre-op
        • Low rate of cross-allergenicity with penicillin-allergic patients
      • Autoimmune hemolytic anemia
      • Disulfiram-like reaction to alcohol
      • Vitamin K deficiency
        • May cause bleeding
      • Increases nephrotoxicity of aminoglycosides
    • Resistance
      • Resistant to penicillinase (beta-lactamase)
        • Esp. later generation (e.g. 3rd generation), explains why they have more gram-negative activity
      • Resistance develops by
        • Structural change in penicillin-binding proteins (transpeptidases)
        • Production of cephalosporinases