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 Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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