Imipenem-cilastatin sodium is hemodialyzable. However, usefulness of this procedure in the overdosage setting is questionable. (See OVERDOSAGE.)

Microbiology

The bactericidal activity of imipenem results from the inhibition of cell wall synthesis. Its greatest affinity is for penicillin binding proteins (PBPs) 1A, 1B, 2, 4, 5 and 6 of Escherichia coli, and 1A, 1B, 2, 4 and 5 of Pseudomonas aeruginosa. The lethal effect is related to binding to PBP 2 and PBP 1B.

Imipenem has a high degree of stability in the presence of beta-lactamases, both penicillinases and cephalosporinases produced by gram-negative and gram-positive bacteria. It is a potent inhibitor of beta-lactamases from certain gram-negative bacteria which are inherently resistant to most beta-lactam antibiotics, e.g., Pseudomonas aeruginosa, Serratia spp., and Enterobacter spp.

Imipenem has in vitro activity against a wide range of gram-positive and gram-negative organisms. Imipenem has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections treated with the intravenous formulation of imipenem-cilastatin sodium as described in the INDICATIONS AND USAGE section.

Gram-positive aerobes

  Enterococcus faecalis (formerly S.faecalis) (NOTE: Imipenem is inactive in vitro against
  Enterococcus faecium [formerly S.faecium].)
  Staphylococcus aureus including penicillinase-producing strains
  Staphylococcus epidermidis including penicillinase-producing strains (NOTE: Methicillin-resistant staphylococci should be reported as resistant to imipenem.)
  Streptococcus agalactiae (Group B streptococci)
  Streptococcus pneumoniae
  Streptococcus pyogenes

Gram-negative aerobes

  Acinetobacter spp.
  Citrobacter spp.
  Enterobacter spp.
  Escherichia coli
  Gardnerella vaginalis
  Haemophilus influenzae
  Haemophilus parainfluenzae
  Klebsiella spp.
  Morganella morganii
  Proteus vulgaris
  Providencia rettgeri
  Pseudomonas aeruginosa(NOTE: Imipenem is inactive in vitro against Xanthomonas (Pseudomonas) maltophilia and some strains of P. cepacia.)
  Serratia spp., including S. marcescens

Gram-positive anaerobes

  Bifidobacterium spp.
  Clostridium spp.
  Eubacterium spp.
  Peptococcus spp.
  Peptostreptococcus spp.
  Propionibacterium spp.

Gram-negative anaerobes

  Bacteroides spp., includingB.fragilis
 Fusobacterium spp.

The following in vitro data are available, but their clinical significance is unknown.

Imipenem exhibits in vitro minimum inhibitory concentrations (MICs) of 4 μg/mL or less against most ( ≥ 90%) strains of the following microorganisms; however, the safety and effectiveness of imipenem in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.

Gram-positive aerobes

  Bacillus spp.
  Listeria monocytogenes
  Nocardia spp.
  Staphylococcus saprophyticus
  Group C streptococci
  Group G streptococci
  Viridans group streptococci

Gram-negative aerobes

  Aeromonas hydrophila
  Alcaligenes spp.
  Capnocytophaga spp.
  Haemophilus ducreyi
  Neisseria gonorrhoeae including penicillinase-producing strains  
  Pasteurella spp.
 Providencia stuartii

Gram-negative anaerobes

  Prevotella bivia
  Prevotella disiens
  Prevotella melaninogenica
  Veillonella spp.

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