Carbapenems

[PHW2:

• Has the broadest spectrum of any class of antimicrobial covering Gram-positive and Gram-negative organisms
• Do not cover MRSA or E faecalis
• Encourage pseudomonas resistance when used as a sole agent

Specific examples

Imipenem

• Very broad spectrum
  * Especially Legionella, and all types of pseudomonas
• Resistant to beta-lactamase but only moderately effective against Clostridia perfringes
• Induce beta-lactamase expression in pseudomonas, which does not alter susceptibility to imipenem but allows substantial protection from other beta-lactams
• Partially metabolised by renal dehydropeptidase-I
  --> Preparation includes cilastatin, which prevents this metabolism
• Excreted unchanged in urine
  --> Can accumulate in renal failure

Side-effects

• Vomiting and diarrhoea (including pseudomembraneous colitis)
• Allergic reactions
• Positive Coomb's test
• Convulsion in patients with pre-existing CNS disorders