Paper II
2016 February (2010 Scheme) · 40 marks · 120 min

Question

Classify cephalosporins. Describe the mechanism of action and clinical uses of ceftriaxone. Which drug can be combined with amoxicillin to treat infection due to beta lactamase producing staph. aureus. ( 2+1+2+1 = 6)

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Answer

Classification of cephalosporins

  • First generation: Cefazolin, Cephalexin
  • Second generation: Cefuroxime, Cefaclor
  • Third generation: Ceftriaxone, Cefotaxime, Ceftazidime
  • Fourth generation: Cefepime
  • Fifth generation: Ceftaroline

Mechanism of action of ceftriaxone

  • Binds to penicillin-binding proteins (PBPs), inhibiting bacterial cell wall transpeptidation (cross-linking of peptidoglycan) — bactericidal, particularly against actively dividing bacteria

Clinical uses of ceftriaxone

  • Meningitis (crosses blood-brain barrier well)
  • Gonorrhoea (single-dose IM therapy)
  • Typhoid fever
  • Community-acquired pneumonia, complicated urinary tract infections
  • Surgical prophylaxis, sepsis (broad Gram-negative and good Gram-positive cover, long half-life allows once-daily dosing)

Drug combined with amoxicillin for beta-lactamase-producing S. aureus

  • Clavulanic acid (Amoxicillin-clavulanate) — clavulanic acid irreversibly inhibits bacterial beta-lactamase, protecting amoxicillin from hydrolysis and restoring efficacy against beta-lactamase-producing organisms

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