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Monobactams and Carbapenims

Monobactams

Monobactams are the beta lactam drugs. One in clinical use is:

Aztreonam
  • Monocyclic β-lactam ring
  • Effective against aerobic gram – rods (esp. pseudomonas)
  • Given I/V – 1-2 g/ 8 hourly
  • Well distributed including CSF
  • Can be given to penecillin-allergic patients

Adverse effects

  1. Skin rash
  2. Deranged LFTs

Uses

  1. Pneumonia
  2. Meningitis
  3. Sepsis

Carbapenems

Beta lactam drugs. There are four drugs clinically available:

  • Imipenem
  • Meropenem
  • Doripenem
  • Etrapenem
Drug Spectrum
Imipenem
  • Gram negative and positive bacteria
  • anerobes
  • E. faecium
  • MRSA
  • C. difficle

 

Meropenem

Doripenem

more active against gram negative aerobes

less active against gram +ve  microorganisms

Etrapenem Same except less against pseudomonas aeruginosa and acinetobacter)

Pharmacokinetics

  • These drugs are given I/V.
  • Distributed to CSF along with other body compartments.
  • Mainly renal excretion.
  • Dose adjustment is done.
  • Imipenem is metabolized in renal tubules by dehydropeptidase enzyme. Cilastatin is dehydropeptidase inhibitor, it may be combined so that enough drug reaches the site of action.
  • Etrapenem is also given I/M. This process is usually painful so combined with 1% lidocaine to avoid pain.

Uses

  1. Mixed aerobic / anaerobic infections especially by resistant strains.
  2. Penicillin resistant pneumococci
  3. Enterobacter infections
  4. Extended-spectrum β-lactamase gram negative organisms
  5. In patients with febrile neutropenia, combined with aminoglycosides.

Adverse effects

Adverse effects are more with Imipenem. Commonly seen are:

  1. Nausea
  2. Vomiting
  3. Diarrhea
  4. Skin rash
  5. In patients of renal impairment, accumulations may lead to seizures
  6. People allergic to penicillin are also allergic to these.

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