Table of Contents
Introduction
Meropenem is a broad-spectrum β-lactam antibiotic belonging to the carbapenem class. It is highly effective against a wide range of Gram-positive, Gram-negative, and anaerobic bacteria, including many resistant organisms. Meropenem is commonly used in severe infections such as sepsis, meningitis, intra-abdominal infections, and hospital-acquired infections. Its bactericidal activity is due to inhibition of bacterial cell wall synthesis.
Mechanism of Action (Step-wise)
- Meropenem penetrates the bacterial cell wall through porin channels (especially in Gram-negative bacteria).
- It binds to penicillin-binding proteins (PBPs) located on the inner membrane of bacterial cell walls.
- These PBPs are enzymes involved in the cross-linking of peptidoglycan strands.
- Meropenem inhibits transpeptidation (cross-linking) of peptidoglycan.
- This weakens the structural integrity of the bacterial cell wall.
- The defective cell wall cannot withstand osmotic pressure.
- This leads to cell swelling and lysis.
- The result is bactericidal activity.
- Meropenem is resistant to most β-lactamases, including extended-spectrum β-lactamases (ESBLs).
A key exam point is that carbapenems like meropenem inhibit cell wall synthesis and are resistant to many β-lactamases.
Pharmacokinetics
Meropenem is administered intravenously because it is not orally bioavailable. It has good tissue penetration, including cerebrospinal fluid, making it useful in meningitis. It has a relatively short half-life and is primarily eliminated by the kidneys. Dose adjustment is required in renal impairment. Unlike imipenem, meropenem has a lower risk of seizures and does not require co-administration with cilastatin.
Clinical Uses
Meropenem is used in severe and life-threatening infections. These include sepsis, meningitis, intra-abdominal infections, complicated urinary tract infections, and hospital-acquired pneumonia. It is particularly valuable in infections caused by multidrug-resistant organisms. It is often reserved for serious infections to prevent development of resistance.
Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, and injection site reactions. Hypersensitivity reactions may occur, especially in patients allergic to other β-lactams. Seizures can occur but are less common compared to imipenem. Long-term use may lead to superinfections such as Clostridioides difficile–associated diarrhea.
Comparative Analysis
| Feature | Meropenem | Imipenem | Ceftriaxone |
|---|---|---|---|
| Class | Carbapenem | Carbapenem | Cephalosporin |
| β-lactamase resistance | High | High | Moderate |
| Need for cilastatin | No | Yes | No |
| Seizure risk | Lower | Higher | Low |
| Spectrum | Very broad | Very broad | Broad |
| Route | IV | IV | IV/IM |
Meropenem differs from imipenem in having a lower seizure risk and not requiring cilastatin. Compared to ceftriaxone, it has a broader spectrum and greater resistance to β-lactamases, making it useful in resistant infections.
MCQs
- Meropenem belongs to which class?
a) Cephalosporins
b) Carbapenems
c) Aminoglycosides
d) Macrolides
Answer: b) Carbapenems
- Meropenem inhibits:
a) Protein synthesis
b) DNA replication
c) Cell wall synthesis
d) RNA synthesis
Answer: c) Cell wall synthesis
- The target of meropenem is:
a) Ribosomes
b) DNA polymerase
c) Penicillin-binding proteins
d) Mitochondria
Answer: c) Penicillin-binding proteins
- Meropenem blocks which process?
a) Transcription
b) Translation
c) Transpeptidation
d) Glycolysis
Answer: c) Transpeptidation
- The result of meropenem action is:
a) Bacteriostasis
b) Bactericidal effect
c) Viral inhibition
d) Immune activation
Answer: b) Bactericidal effect
- Meropenem is administered via:
a) Oral route
b) Intravenous route
c) Subcutaneous route
d) Inhalation
Answer: b) Intravenous route
- Meropenem is effective against:
a) Only Gram-positive bacteria
b) Only Gram-negative bacteria
c) Broad spectrum bacteria
d) Only fungi
Answer: c) Broad spectrum bacteria
- Meropenem is resistant to:
a) Proteinases
b) β-lactamases
c) Lipases
d) Oxidases
Answer: b) β-lactamases
- Compared to imipenem, meropenem has:
a) Higher seizure risk
b) Lower seizure risk
c) Same risk
d) No effect
Answer: b) Lower seizure risk
- Meropenem is eliminated mainly by:
a) Liver
b) Kidney
c) Lungs
d) Skin
Answer: b) Kidney
- A common adverse effect is:
a) Hypoglycemia
b) Diarrhea
c) Hypercalcemia
d) Bradycardia
Answer: b) Diarrhea
- Meropenem is used in:
a) Mild infections only
b) Severe infections
c) Viral infections
d) Fungal infections
Answer: b) Severe infections
FAQs
What is the mechanism of action of meropenem?
It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins.
Is meropenem bactericidal or bacteriostatic?
It is bactericidal.
Why is meropenem resistant to β-lactamases?
Its structure makes it stable against most β-lactamase enzymes.
Does meropenem require cilastatin?
No, unlike imipenem.
Can meropenem be used in meningitis?
Yes, it penetrates cerebrospinal fluid effectively.
What is the main elimination route of meropenem?
Renal excretion.
References
Goodman & Gilman’s The Pharmacological Basis of Therapeutics – Antimicrobial Agents
https://accessmedicine.mhmedical.com/book.aspx?bookid=3191
Katzung: Basic and Clinical Pharmacology – β-lactam Antibiotics
https://accessmedicine.mhmedical.com/content.aspx?bookid=3382
Tripathi: Essentials of Medical Pharmacology – Antibiotics
https://www.jaypeedigital.com
Harrison’s Principles of Internal Medicine – Infectious Diseases
https://accessmedicine.mhmedical.com
