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
- Skin rash
- Deranged LFTs
Uses
- Pneumonia
- Meningitis
- Sepsis
Carbapenems
Beta lactam drugs. There are four drugs clinically available:
- Imipenem
- Meropenem
- Doripenem
- Etrapenem
| Drug | Spectrum |
| Imipenem | Gram negative and positive bacteriaanerobesE. faeciumMRSAC. difficle |
| MeropenemDoripenem | more active against gram negative aerobesless 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
- Mixed aerobic / anaerobic infections especially by resistant strains.
- Penicillin resistant pneumococci
- Enterobacter infections
- Extended-spectrum β-lactamase gram negative organisms
- In patients with febrile neutropenia, combined with aminoglycosides.
Adverse effects
Adverse effects are more with Imipenem. Commonly seen are:
- Nausea
- Vomiting
- Diarrhea
- Skin rash
- In patients of renal impairment, accumulations may lead to seizures
- People allergic to penicillin are also allergic to these.