1. Clinical Overview
Meropenem is a broad-spectrum, bactericidal carbapenem antibiotic. It is a beta-lactam antibiotic with a structure that confers high stability against most beta-lactamases, including extended-spectrum beta-lactamases (ESBLs). It is a cornerstone of empiric therapy for severe, life-threatening infections in the Indian hospital setting, particularly in ICUs, due to its reliable activity against a wide range of Gram-positive, Gram-negative, and anaerobic bacteria.
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapid; bactericidal action begins immediately upon reaching effective tissue concentrations. | Approximately 6-8 hours, necessitating dosing every 8 hours for most infections. | Not applicable; administered exclusively via intravenous (IV) infusion or bolus injection. |
2. Mechanism of Action
Meropenem exerts its bactericidal effect by inhibiting bacterial cell wall synthesis. It has a high affinity for penicillin-binding proteins (PBPs), particularly PBP-2 in Escherichia coli and Pseudomonas aeruginosa, and PBP-1 in Staphylococcus aureus. Binding to these essential enzymes disrupts the final transpeptidation step of peptidoglycan synthesis, leading to osmotic instability and cell lysis.
3. Indications & Uses
- Complicated intra-abdominal infections (cIAI)
- Complicated skin and skin structure infections (cSSSI)
- Bacterial meningitis (in pediatric patients >3 months)
- Complicated urinary tract infections (cUTI) including pyelonephritis
- Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP)
- Empiric therapy for febrile neutropenia
4. Dosage & Administration
Adult Dosage: 1g (1000mg) administered intravenously every 8 hours. For meningitis: 2g every 8 hours.
Administration: For IV infusion: Reconstitute 1g vial with 20 mL Water for Injection. Shake to dissolve. Further dilute in 50-250 mL of compatible IV fluid (0.9% Sodium Chloride or 5% Dextrose). Infuse over 15-30 minutes. For IV bolus: Reconstitute as above and administer over 3-5 minutes (5-20 mL solution). NOT for intramuscular use.
5. Side Effects
Common side effects may include:
- Diarrhea (including Clostridioides difficile-associated diarrhea)
- Nausea and vomiting
- Headache
- Injection site reactions (pain, inflammation, phlebitis)
- Rash and pruritus
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Probenecid | Competitively inhibits renal tubular secretion of meropenem, increasing and prolonging meropenem plasma levels. Not recommended for co-administration. | Major |
| Valproic Acid / Valproate | Meropenem significantly reduces serum valproic acid levels by up to 60-100%, potentially leading to loss of seizure control. Avoid concomitant use; use alternative antibiotics or monitor valproate levels closely. | Major |
| Other nephrotoxic drugs (e.g., Aminoglycosides, Vancomycin, Loop diuretics) | Increased risk of nephrotoxicity. Monitor renal function closely. | Moderate |
| Warfarin | Potential for increased anticoagulant effect due to altered gut flora and possible effects on vitamin K. Monitor INR closely. | Moderate |
7. Patient Counselling
- Do complete the full course of therapy as prescribed, even if you feel better.
- Do inform all your doctors about any history of allergies, especially to penicillin or other antibiotics.
- Do report any severe diarrhea, even if it occurs weeks after finishing the antibiotic.
- Don't skip doses.
- Don't use this medicine for colds, flu, or other viral infections.
8. Toxicology & Storage
Overdose: Symptoms may include exaggerated pharmacological effects such as seizures (especially in patients with renal failure), paresthesia, encephalopathy, and neuromuscular excitability. Gastrointestinal effects like nausea and diarrhea may occur.
Storage: Unreconstituted vials: Store below 25°C. Protect from light. Reconstituted Solution: Chemical and physical stability of the reconstituted solution in Water for Injection has been demonstrated for up to 3 hours at up to 25°C. Solutions diluted for infusion in 0.9% Sodium Chloride or 5% Dextrose are stable for up to 4 hours at up to 25°C or 24 hours if stored under refrigeration (2-8°C). Do not freeze. Use immediately after preparation is recommended. Discard any unused portion.