Pharm 101: Ceftriaxone

Class

Third generation cephalosporin
Other third generation cephalosporins: cefotaxime, ceftazidime, cefoperazone

Pharmacodynamics
  • Beta lactam antibiotic
  • Inhibits transpeptidation reaction of bacterial cell wall synthesis
  • Halts peptidoglycan synthesis, leading to inhibition of bacterial growth, and ultimately cell death (bacteriocidal)
  • Beta-lactam antibiotics kill bacterial cells only when they are actively growing and synthesising cell wall
Pharmacokinetics
  • IV administration
  • Crosses the blood-brain barrier
  • Half-life 7-8 hours, allowing once daily administration 15-50mg/kg
  • Mixed clearance with biliary excretion, therefore no dose adjustment required in renal failure
Antimicrobial activity
  • Expanded gram negative coverage
  • Less active against Staph than first/second generation cephalosporins
  • Not usually degraded by bacterial beta-lactamases, therefore broader spectrum of activity
  • Effective against:
    • Beta lactamase producing strains of Haemophilus and Neisseria
    • Penicillin-resistant pneumococcus
    • Citrobacter
  • Not effective against:
    • Enterobacter
    • Pseudomonas
    • L monocytogenes
Adverse effects of cephalosporins
  • Allergy:
    • Cross-allergenicity between penicillins and cephalosporins is ~1%
  • Toxicity:
    • Thrombophlebitis after IVI
    • Renal toxicity: interstitial nephritis, tubular necrosis (rare)
  • Methylthiotetrazole-containing agents (cefotetan, cefoperazone) may cause bleeding disorders and disulfiram-like reactions
Precautions/contraindications
  • Penicillin anaphylaxis
  • Drug interactions:
    • Warfarin: eliminate bacteria that produce Vitamin K and thus can increase INR
Further reading
References
Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS CCPU (RCE, Biliary, DVT, E-FAST, AAA) Rob is an Emergency Medicine Advanced Trainee based in Melbourne, Australia. He has special interests in medical education, ECG interpretation, and the use of diagnostic and procedural ultrasound in the undifferentiated and unwell patient.

Follow him on twitter: @rob_buttner | ECG Library |

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