1. Clinical Overview
Ertapenem is a parenteral, broad-spectrum, 1-beta-methyl carbapenem antibiotic. It is structurally similar to meropenem but has a longer half-life, allowing for once-daily administration. It is effective against a wide range of Gram-positive and Gram-negative aerobic and anaerobic bacteria, including many Extended-Spectrum Beta-Lactamase (ESBL)-producing organisms, but lacks activity against Pseudomonas aeruginosa and Acinetobacter species. It is a critical agent in the Indian hospital setting for managing moderate to severe community-acquired and mixed infections.
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapid; bactericidal concentrations achieved within 30 minutes of IV infusion completion. | Approximately 24 hours, supporting once-daily dosing. | Not applicable (IV/IM administration). Intramuscular bioavailability is approximately 90%. |
2. Mechanism of Action
Ertapenem exerts bactericidal activity by inhibiting bacterial cell wall synthesis. It has a high affinity for Penicillin-Binding Proteins (PBPs), particularly PBP-2 in Gram-negative bacteria and PBP-1, PBP-2, and PBP-3 in Gram-positive bacteria. Binding to these enzymes inhibits 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)
- Community-Acquired Pneumonia (CAP)
- Complicated Urinary Tract Infections (cUTI) including pyelonephritis
- Acute Pelvic Infections (including postpartum endomyometritis, septic abortion, and postsurgical gynecological infections)
4. Dosage & Administration
Adult Dosage: 1 gram administered once daily by intravenous infusion over 30 minutes or by intramuscular injection.
Administration: IV: Reconstitute 1g vial with 10 mL of Water for Injection, NaCl 0.9%, or Bacteriostatic Water for Injection. Shake well. Further dilute in 50 mL of NaCl 0.9% ONLY. Infuse over 30 minutes. DO NOT use dextrose (D5W) as diluent. IM: Reconstitute 1g vial with 3.2 mL of 1% lidocaine HCl injection (without epinephrine). Shake thoroughly. Administer by deep intramuscular injection into a large muscle mass. Do not administer IV. IM and IV solutions are NOT interchangeable.
5. Side Effects
Common side effects may include:
- Diarrhea (including Clostridioides difficile-associated diarrhea)
- Infusion site reactions (phlebitis, pain, erythema)
- Injection site reactions (pain, induration) for IM route
- Nausea
- Headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Probenecid | Competitively inhibits renal tubular secretion of ertapenem, increasing its plasma concentration and half-life. Coadministration is not recommended. | Major |
| Valproic Acid / Divalproex Sodium | Ertapenem significantly reduces serum valproic acid levels (by up to 90%), leading to loss of seizure control. Avoid concomitant use. Use alternative antibiotics or anticonvulsants. | Major |
| Other seizure threshold-lowering drugs (e.g., Theophylline, Fluoroquinolones) | Increased risk of seizures. Monitor closely. | Moderate |
| Warfarin | Potential for increased INR 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 even if you feel better.
- Do inform all your doctors about any allergy to penicillin, cephalosporin, or other drugs.
- Do report severe diarrhea, even if it occurs weeks after finishing the antibiotic.
- Do not mix or reconstitute the medicine yourself; it must be prepared by a trained healthcare professional.
- Do not use dextrose solutions for IV infusion.
8. Toxicology & Storage
Overdose: Symptoms may include seizures, neuromuscular hypersensitivity, and exaggerated side effects like nausea, diarrhea, and dizziness. In case of accidental overdose, seizures should be treated with benzodiazepines.
Storage: Unreconstituted vials: Store below 25°C. Protect from light. Reconstituted solution (IV): When reconstituted with Water for Injection or NaCl 0.9%, the solution may be stored at room temperature (25°C) for up to 6 hours, or under refrigeration (2-8°C) for up to 24 hours. Do not freeze. Use within 4 hours if diluted in NaCl 0.9% for infusion. Reconstituted solution (IM with lidocaine): Use immediately. Discard any unused portion. Do not store.