The current slide include pharmacology of Monobactams and Carbapenems including drugs Aztreonam, imipenem, Meropenem and Faropenem.

1. MONOBACTAMS AND
CARBAPENEMS
Anusha Shaji, B.Pharm, M.Pharm
Assistant Professor
Department of Pharmacology
Nirmala College of Pharmacy,
Muvattupuzha, Ernakulam

2. Monobactams: Aztreonam
Novel beta lactam antibiotic
In which the other ring is missing → hence monobactam
Acts by binding to specific Penicillin Binding Proteins (PBPs)
At very low concentrations: It inhibits gram negative enteric bacilli and
H.influenzae
At moderate concentrations: inhibits Pseudomonas
Does not inhibit gram positive cocci or faecal anaerobes
Resistant to gram negative beta lactamases
The main indications of aztreonam are hospital acquired infections
originating from urinary, biliary, gastrointestinal and female genital tracts.
Spectrum resembling aminoglycosides

3. The most prominent feature of aztreonam is the lack of cross sensitivity
with other beta lactam antibiotics
↓
Permitting its use in patients allergic to penicillin or cephalosporins
Adverse effects: Rashes and rise in serum aminotransferases
Plasma half life: 1.8 hour
Eliminated unchanged in urine
Dose: 0.5- 2 g i.m or i.v 6-12 hourly

4. Carbapenems
Eg: Imipenem, Meropenem, Faropenem, Doripenem
Imipenem
A derivative of thienamycin
Extremely potent
Broad spectrum beta-lactam antibiotic
Range of activity include:
* Gram positive cocci
* Enterobacteriaceae
* Ps. aeruginosa
* Listeria
* Bact. fragilis (anaerobes)
* Cl. difficile (anaerobes)
Resistant to most beta- lactamases

5. It inhibits penicillinase producing staphylococci.
Rapid hydrolysis by dehydropeptidase I located on the brush border of renal
tubular cells
↓
Hence it is given in combination with cilastatin
Cilastatin
A reversible inhibitor of dehydropeptidase I
It has matched pharmacokinetics with imipenem
Plasma half life of both is 1 hour
Imipenem + Cilastatin Dose: 0.5 g iv 6 hourly (maximum 4 g/day)
↓
Effective in a wide range of hospital acquired repiratory, urinary, abdominal,
pelvic, skin and soft tissue infections including cancer, AIDs and neutropenic
patients.

6. For Ps. aeruginosa infections – Imipenem+ Gentamicin
At higher doses: Imipenem induce seizures
Side effects: Diarrhoea, vomiting, skin rashes and other hypersensitivity
reactions
Meropenem
Newer carbapenem
It is not hydrolysed by renal peptidase
Does not need to be protected by cilastatin
Active against both gram positive and negative bacteria, aerobes as well as
anaerobes
More potent on gram negative aerobes (especially Ps. aeruginosa)
Less potent on gram positive cocci

7. Use
For the treatment of serious nosocomial infections like septicaemia, febrile
neutropenia, intraabdominal and pelvic infections, etc. caused by
cephalosporin resistant bacteria and diabetic foot.
For Ps. aeruginosa infections: Combination of Meropenem with
Aminoglycoside
Adverse effects
Diarrhoea, skin rashes, vomiting and other hypersensitivity reactions
Less likely to cause seizures
Dose: 0.5- 2.0 g (10-40 mg/kg) by slow i.v injection 8 hourly

8. Faropenem
Carbapenem beta- lactam antibiotic
Orally active against both gram positive and gram negative bacteria, including
some anaerobes
Highly susceptible organisms: Strep. pneumoniae, H. influenzae, Moraxella
catarrhalis
Mainly used in respiratory, ENT and genitourinary infections
Side effects: diarrhoea, abdominal pain, nausea and rashes
Dose: 150-300mg oral TDS