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 (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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