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cephalosporins

cephalosporins

introduction

  • similar to penicillins, cephalosporins are beta lactam ring antibiotics which kill bacteria by compromising their cell wall
  • generally NOT active against LAME : Listeria, Atypicals (including Mycoplasma and Chlamydia), MRSA, enterococci
  • Poorly cross BBB and not used in Rx of meningitis except 3rd gens.

classes of cephalosporins

1st generation:

  • mainly for Gram +ves & some Gram -ves
  • eg. cephalexin, cephazolin/cefazolin

2nd generation:

  • less Gram +ve cover, more Gram -ve cover
  • some active against B. fragilis & thus used in mixed anaerobe infections such as peritonitis, diverticulitis:
    • eg. cefotetan, cefoxitin
  • others active against H. influenzae:
    • eg. cefaclor, cefamandole, cefuroxime, cefotetan, cefoxitin

3rd generation

  • expanded Gram -ve cover, even less Gram +ve cover
  • cross BBB adequately for Rx of meningitis
  • used in H.influenzae septicaemia
  • eg. cefotaxime, ceftriaxone, ceftazidime

4th generation

  • some cross BBB and can be used in meningitis
  • similar activity against Gram-positive organisms as first-generation cephalosporins
  • are zwitterions that can penetrate the outer membrane of Gram-negative bacteria
  • greater resistance to beta-lactamases than the third-generation cephalosporins
  • can be used against Pseudomonas aeruginosa
  • examples:
    • cefclidine, cefepime, cefpirome
    • oxacephems: flomoxef

"5th generation"

  • ceftobiprole:
    • powerful antipseudomonal characteristics and appears to be less susceptible to development of resistance
  • ceftaroline:
    • introduced in Australia in 2013
    • does not have the anti-pseudomonal or VRE coverage of ceftobiprole
    • less effective against some Gram negatives
    • binds to the altered penicillin binding proteins produced by certain penicillin resistant bacteria
    • broad spectrum coverage includes E. coli, H. influenzae, Klebsiella pneumoniae, MRSA, penicillin non-susceptible Str. pneumoniae
    • used to Rx skin, soft tissue infections and community acquired pneumonia (with an adjunctive antibiotic such as clarithromycin, and clinical cure rates were a touch better than for ceftriaxone with clarithromycin)
    • 90% renal excreted, half life 2.5hrs
    • 10% develop a positive Coombs test
    • usual adult dose: 600mg iv infusion over 1hr bd
cephalosporins.txt · Last modified: 2017/04/03 09:06 (external edit)