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Laboratory data which differentiate meropenem and imipenem
1Zeneca Pharmaceuticals, Macclesfield, Cheshire, UK.
Abstract:
Meropenem and imipenem are carbapenems which are distinguishable from all other currently available beta-lactam antibiotics by breadth of antibacterial spectrum and stability to beta-lactamases, but can be differentiated one from another. Meropenem is relatively stable to human renal dehydropeptidase-I (DHP-I); it does not require to be co-administered with cilastatin and consequently, unlike imipenem, will be administered as a single agent. In vitro both meropenem and imipenem are active against almost all clinically important aerobic and anaerobic bacteria. Differences in potency are seen but few may be of clinical significance: imipenem is more active against enterococci and meropenem is more active against Pseudomonas aeruginosa, Pseudomonas cepacia, Haemophilus influenzae and Proteus, Morganella and Providencia species. The primary target of imipenem is PBP2 in P. aeruginosa whilst meropenem has high affinity for both PBP2 and 3; this may contribute to greater potency against this organism. Laboratory evaluations predict that meropenem will not be seizurogenic, which combined with activity against likely pathogens, identified its potential for the treatment of bacterial meningitis. This has been investigated in a guinea-pig model in which meropenem exhibited potent activity against the common meningeal pathogens and also infections caused by penicillin-resistant Streptococcus pneumoniae or Listeria monocytogenes. Clinical experience will determine the significance of these differences.
Insights
Meropenem and imipenem are broad-spectrum carbapenem antibiotics. Meropenem shows enhanced activity against certain bacteria and potential for treating meningitis, unlike imipenem.
Area of Science:
- Pharmacology
- Microbiology
- Infectious Diseases
Background:
- Meropenem and imipenem are carbapenem antibiotics with broad antibacterial spectra and beta-lactamase stability.
- Carbapenems differ in their activity against specific pathogens and their pharmacokinetic properties.
Purpose of the Study:
- To compare the antibacterial spectrum, stability, and clinical potential of meropenem and imipenem.
- To evaluate meropenem's efficacy in treating bacterial meningitis.
Main Methods:
- In vitro susceptibility testing against various aerobic and anaerobic bacteria.
- Assessment of stability to human renal dehydropeptidase-I (DHP-I).
- Evaluation in a guinea-pig model of bacterial meningitis.
Main Results:
- Both agents are active against most clinically important bacteria; meropenem shows greater potency against Pseudomonas aeruginosa, Pseudomonas cepacia, Haemophilus influenzae, Proteus, Morganella, and Providencia species.
- Meropenem is stable to DHP-I and does not require co-administration with cilastatin.
- Meropenem demonstrated potent activity against common meningeal pathogens in a guinea-pig meningitis model.
Conclusions:
- Meropenem offers a distinct profile from imipenem, with potential advantages in treating specific infections, including bacterial meningitis.
- Meropenem's stability to DHP-I and broad spectrum suggest its utility as a single-agent therapy.
- Further clinical studies are needed to confirm the significance of observed differences in efficacy.