Cephalosporin

Aka: Cephalosporin

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II. General

  1. Spectrum changes from first to third generation
    1. First Generation: Better Gram Positive Cocci coverage
    2. Third Generation: Better Gram Negative Rod coverage

III. Contraindications

  1. Drug allergy to other Cephalosporin
  2. Type I Hypersensitivity Reaction to a Penicillin
    1. Less than 10% of those who report Penicillin Allergy actually have a Penicillin Allergy
    2. Cross reactivity was originally over-estimated as high as 10% in the 1960s
      1. Attributed to cross contamination from co-production of Cephalosporins and Penicillins in the same factory
    3. Penicillin Allergy has only an overall 1-2% risk of cross-reactivity with Cephalosporins
      1. Herbert (2000) West J Med 172(5): 341 [PubMed]
    4. Penicillin Anaphylaxis confers a 0.001% risk of Anaphylaxis to Cephalosporins
      1. Apter (2006) Am J Med 119(4):354.e11-9 [PubMed]
    5. Cross reactivity appears primarily limited to First Generation Cephalosporins and Penicillins
      1. Third Generation Cephalosporins have minimal to no allergy cross reactivity
      2. Campagna (2012) J Emerg Med 42(5): 612-20 [PubMed]
    6. Aminopenicillins (Amoxicillin and Ampicillin) allergy and allergy to first and Second Generation Cephalosporins: High
      1. R1-side chain of Aminopenicillins are similar to first and Second Generation Cephalosporins (esp. Cefprozil, Cefadroxil)
      2. Reaction rate is as high as 27% for Cefadroxil
      3. Campagna (2012) J Emerg Med 42(5): 612-20 [PubMed]

IV. Mechanism: Beta Lactams

  1. See Beta Lactam
  2. Beta Lactam Structure
    1. Penicillins, Cephalosporins, Carbapenems and Monobactams are all Beta Lactams
    2. Beta Lactams share a 4-membered ring structure (3 Carbons, 1 Nitrogen)
  3. Bacteria (Gram Positive and negative) have cell walls that contain peptidoglycans
    1. Peptidoglycans are repeated Disaccharides cross-linked with Amino Acids
    2. Transpeptidase cross-links peptidoglycan mesh in the synthesis of the Bacterial cell wall
  4. Beta Lactams bind and inactivate Transpeptidase (also known as Penicillin Binding Protein)
    1. Transpeptidase enzymes are located on the Bacteria's inner cytoplasmic membrane
    2. Beta Lactams must traverse outer cell wall layers to bind Transpeptidase
    3. Beta-Lactam's inhibition of Transpeptidase results in lysis and death of the Bacterial cell
  5. Beta-Lactams are inactivated by the enzyme Beta-Lactamase (Penicillinase, Cephalosporinase)
    1. Beta-Lactamase is produced by beta-lactam resistant Bacteria
    2. Beta Lactamase cleaves a carbon-nitrogen bond in the 4 member Beta Lactam ring
    3. Cephalosporins were developed with a side chain at the CN bond to block Penicillinases
      1. However Bacteria have since developed resistance via Cephalosporinases
      2. MRSA and Enterococcus are also Cephalosporin resistant
  6. Other Beta Lactam Resistance Mechanisms
    1. Altered Transpeptidase Structure
      1. Prevents binding by Beta Lactams
      2. Example: Methicillin Resistant Staphylococcus Aureus (MRSA)
    2. Gram Negative Bacteria are protected by an additional lipid bilayer
      1. Molecules pass through this layer via porin channels (e.g. OmpF, OmpC) to access the cell wall
      2. Porin channels retrict larger molecules, and not all Beta Lactams can pass through porins
      3. Other Gram Negative Bacteria may down regulate porin channels to limit entry
    3. Beta Lactam Efflux Pumps
      1. Some Bacteria are able to actively pump the Beta Lactam out before transpeptidase binding
      2. Examples: E. coli (AcrAB-TolC) and Pseudomonas Aeruginosa (MexAB-OprM)
  7. Beta-Lactamase inhibitors have been developed to counter Beta Lactam resistance
    1. Amoxicillin-clavulanic acid (Augmentin)
    2. Ampicillin-Sulbactam (Unasyn)
    3. Ceftazidime-Avibactam

V. Class: First Generation Cephalosporins

  1. Oral Agents
    1. Cephalexin (Keflex)
    2. Cephradine (Velosef)
    3. Cefadroxil (Duricef)
  2. Parenteral Agents
    1. Cefazolin (Ancef)
  3. Organisms covered
    1. Gram Positive Cocci (Streptococcus and MSSA)
    2. EKP Gram Negative Bacteria

VI. Class: Second Generation Cephalosporins

  1. Second Generation Broad-spectrum Cephalosporins
    1. Oral Agents
      1. Loracarbef (Lorabid)
      2. Cefprozil (Cefzil)
      3. Cefuroxime (Ceftin, Zinacef)
      4. Cefaclor (Ceclor)
    2. Organisms Covered
      1. Gram Positive Cocci
      2. EKP Gram Negative Bacteria (e.g. Streptococcus Pneumoniae)
      3. Gram Negative Coccobacilli (H. Influenzae) or Diplococci (M. catarrhalis)
  2. Second Generation Anti-anaerobe Cephalosporins
    1. Parenteral Agents
      1. Cefoxitin
      2. Cefotetan
      3. Cefamandole
    2. Organisms Covered
      1. Anaerobic coverage (differentiates from Second Generation Broad-spectrum Cephalosporins)
        1. Bacteroides fragilis
        2. Growing Anaerobe resistance
      2. Gram Positive Bacteria
        1. Less than Second Generation Broad-spectrum Cephalosporins (e.g. Cefuroxime)
      3. Gram Negative Bacteria

VII. Class: Third Generation Cephalosporins

  1. Third Generation Broad-Spectrum Cephalosporins
    1. Oral agents
      1. Cefixime (Suprax)
        1. Only indication is for Gonorrhea
      2. Cefpodoxime (Vantin)
        1. Does not cover Enterobacter or Pseudomonas
      3. Cefdinir (Omnicef)
    2. Parenteral agents
      1. Cefotaxime (Claforan)
      2. Ceftizoxime (Cefizox)
      3. Ceftriaxone (Rocephin)
    3. Organisms Covered
      1. Gram Positive Cocci
      2. EKP Gram Negative Bacteria
      3. ESP Gram Negative Bacteria
      4. No Pseudomonas activity
  2. Third Generation Anti-Pseudomonal Cephalosporins
    1. Parenteral Agents
      1. Ceftazidime (Fortaz)
    2. Organisms Covered
      1. Pseudomonas
      2. EKP Gram Negative Bacteria
      3. ESP Gram Negative Bacteria
      4. Poor Gram Positive Cocci coverage
      5. No Coccobacilli coverage

VIII. Class: Fourth Generation Cephalosporins

  1. Parenteral Agents
    1. Cefepime (Maxipime)
  2. Organisms Covered
    1. Broad spectrum Gram-positive and Gram-negative organisms building on third generation coverage
    2. Beta-Lactamase resistant organisms
    3. Pseudomonas coverage

IX. Class: Fifth Generation Cephalosporins

  1. Parenteral Agents
    1. Ceftaroline
    2. Ceftolozane and Tazobactam (Zerbaxa)
    3. Ceftazidime and Avibactam (Avycaz)
  2. Organisms Covered
    1. Broad spectrum Gram-positive and Gram-negative organisms building on third generation coverage
    2. Pseudomonas coverage
    3. Methicillin Resistant Staphylococcus Aureus (MRSA)

X. Dosing: Adults

  1. Almost all Cephalosporins
    1. Typical Dose: 1-2 grams IV q8h
  2. Exceptions
    1. Ceftriaxone 1-2 grams IV q24 hours
    2. Cefotetan 1-2 grams IV q12 hours

XI. Dosing: Children

  1. Almost all Cephalosporins
    1. Typical dose: 100-200 mg/kg/day divided q8 hours
  2. Exceptions
    1. Ceftriaxone 75-100 mg/kg/day q24 hours

XII. Prevention: Reducing Adverse Effects

  1. Least Diarrhea
    1. Loracarbef (Lorabid)
    2. Cefprozil (Cefzil)
  2. Best taste
    1. Loracarbef (Lorabid)
    2. Cefixime (Suprax)
    3. Cefpodoxime (Vantin, taste applies to under age 2 years)

XIII. References

  1. Pensa and Hayes in Swadron (2022) EM:Rap 22(9): 6-8

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