Ertapenem
Ertapenem is a broad-spectrum **carbapenem antibiotic** structurally similar to imipenem and meropenem, but with a narrower spectrum of activity. * **Key Difference:** Unlike other carbapenems, it is **not effective against *Pseudomonas aeruginosa* or *Acinetobacter***. * **Clinical Utility:** It is particularly useful for treating resistant gram-negative bacterial infections, especially when aminoglycosides are contraindicated (e.g., renal failure) or ineffective, and when meropenem is unavailable. * **Veterinary Use:** Currently, there is very limited information regarding its use in dogs and cats; it is considered **investigational** in veterinary medicine. * **Advantage:** It has a longer half-life in humans, potentially allowing for once-daily dosing, though twice-daily dosing is currently suggested for small animals.
Mechanism: Ertapenem is a **beta-lactam antibiotic** that exerts its bactericidal effect by inhibiting bacterial cell wall synthesis. * **Mechanism:** It binds to **penicillin-binding proteins (PBPs)** → inhibits peptidoglycan cross-linking → weakens the bacterial cell wall → causes cell lysis and death. * **Enzyme Stability:** It is highly resistant to degradation by most beta-lactamases, including penicillinases and cephalosporinases. * **Renal Stability:** Unlike imipenem, ertapenem is stable against renal **dehydropeptidase I**, meaning it does *not* require co-administration with cilastatin.
Dosing by species
- Susceptible infections (Investigational) · 15 mg/kg IV or IM every 12 hours (not to exceed a daily dosage of 1 gram) · IV/IM · q12h · Monitor literature for additional data.
- Susceptible infections (Investigational) · 15 mg/kg IV or IM every 12 hours (not to exceed a daily dosage of 1 gram) · IV/IM · q12h · Monitor literature for additional data.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hypersensitivity to ertapenem or other carbapenems
- History of anaphylaxis to any beta-lactam antibiotic
- Hypersensitivity to lidocaine or amide-type local anesthetics (if using 1% lidocaine as an IM diluent)
Adverse effects
- Injection site reactions (most common in humans)
- Gastrointestinal effects (nausea, vomiting, diarrhea)
- Headache
- Tachycardia
- Hypersensitivity reactions (rare)
- CNS effects (hallucinations, agitation, seizures - rare)
Drug interactions
- Probenecid · Can increase ertapenem AUC by 25% and elimination half-life by about 20%. Not recommended to be used concurrently to extend half-life.
Monitoring
- Clinical efficacy (WBC count, resolution of fever, etc.)
- Adverse effects (GI signs, neurotoxicity, hypersensitivity)
- Hepatic, hematopoietic, and renal function (suggested for periodic assessment during prolonged use)
Overdose
Inadvertent overdoses are unlikely. In humans, a 3-gram IV dose caused an increased incidence of nausea and diarrhea. If overdose occurs and adverse effects are noted, treat supportively.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.