Carbapenem & Monobactum



  • Are beta-lactam antibiotics.
  • Beta-lactam antibiotics – Drugs containing ßlactam ring in their structure.
  • Drugs:
    • Penicillins
    • Cephalosporins (above both discussed separately)
    • Monobactams e.g. aztreonam
    • Carbapenems e.g. imipenem

General features:

  • All ß-lactam antibiotics are bactericidal drugs.
  • MOA: 
    • Bind to specific receptors (penicillin-binding proteins; PBPs) on bacterial cell membrane.
    • Inhibits transpeptidase enzyme
    • Responsible for peptidoglycan chain cross-linking.
    • Bacteria formed in drug presence are without cell wall –> Dies due to water imbibition. (cell wall provides turgidity).

I) Monobactams:

  • Only beta-lactam antibiotic for patients with severe penicillin or cephalosporins allergy
  • Since not cross allergenic.
  • Drugs: Aztreonam.
    • Active against β-lactamase producing gram negative rods including Pseudomonas.
    • No activity against gram-positive organisms or anaerobes.
    • Administered i.v.
    • Prolonged half-life in renal failure.

II) Carbapenems:

  • Are β-lactamase resistant.
  • DOC for Enterobacter, Klebsiella & acinetobacter species.
  • Wide spectrum of activity – Including gram-positive cocci, gram-negative rods & anaerobes.
  • Only β-lactams, reliably efficacious against ESBL (extended spectrum β-lactamase) producing organisms.

Drugs: Imipenem, doripenem, meropenem & ertapenem.


  • For Pseudomonas treatment:
    • Meropenem – Most active & Ertapenem – least.
    • Should be combined with aminoglycosides.

Individual drug description:

  • Imipenem:
    • Rapidly inactivated by renal dehydropeptidase I enzyme.
    • Always combined with cilastatin.
    • Increases imipenem half-life.
    • Inhibits nephrotoxic metabolite formation.
  • (Note on cilastatin: Inhibitor of renal dehydropeptidase I enzyme).
  • Adverse effects:
    • Imipenem-cilastatin combination include seizures & gastrointestinal distress (Main).
  • Meropenem, doripenem & ertapenem:
    • Not metabolized by renal dehydropeptidase.
    • Hence, less likely seizures.
  • Ertapenem:
    • Very long acting.
    • Inactive against Pseudomonas.
  • Loracarbef:
    • Chemically similar to cefaclor.
    • Oral drug.
    • Overdose can cause seizures.

Exam Important

  • Carbapenem & Monobactum are beta-lactum antibiotics.
  • Aztreonam is a Monobactam.
  • Imipenem is a Carbapenem.
  • All ß-lactam antibiotics are bactericidal drugs.
  • Monobactam is only beta-lactam antibiotic for patients with severe penicillin or cephalosporins allergy, since not cross allergenic.
  • Aztreonam is active against β-lactamase producing gram-negative rods, including Pseudomonas.
  • Carbapenem is β-lactamase resistant which is DOC for Enterobacter, Klebsiella & acinetobacter species.
  • Carbapenem is only β-lactams, reliably efficacious against ESBL (extended spectrum β-lactamase) producing organisms.
  • Imipenem, doripenem, meropenem & ertapenem are all carbapenem.
  • Meropenem is a most active & Ertapenem is least active carbapenem.
  • Imipenem is always combined with cilastatin because it gets rapidly inactivated by renal dehydropeptidase I enzyme.
  • Cilastatin is an inhibitor of renal dehydropeptidase I enzyme.
  • Imipenem-cilastatin combination mainly causes seizures & gastrointestinal distress (adverse effects).
  • Meropenem, doripenem & ertapenem are not metabolized by renal dehydropeptidase, hence, less likely seizures.
  • Ertapenem is very long-acting & are inactive against Pseudomonas.


Don’t Forget to Solve all the previous Year Question asked on CARBAPENEM & MONOBACTUM

Module Below Start Quiz

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