Meropenem
Also known as: Merrem I.V. · Meronem · Meropen · Optinem · Zeropenem · ICI-194660 · SM-7338
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Bacteremia/sepsis | 24 mg/kg IV q24h (once daily) or 12 mg/kg SC q8h | IV/SC | q24h or q8h | — | 🌎 NA |
| UTI | 12 mg/kg SC q12h | SC | q12h | — | 🌎 NA |
| CNS infections | 40 mg/kg IV or SC q8h | IV/SC | q8h | — | 🌎 NA |
| Systemic infections | 12 mg/kg q8h SC or 24 mg/kg IV q24h (once daily) | SC/IV | q8h or q24h | — | 🌎 NA |
| Urinary tract infections | 12 mg/kg q12h SC | SC | q12h | — | 🌎 NA |
| Susceptible infections (Small dogs) | 125 mg (total dose) q8h IV or SC | IV/SC | q8h | — | 🌎 NA |
| Susceptible infections (Medium dogs) | 250 mg q8h IV or SC | IV/SC | q8h | — | 🌎 NA |
| Susceptible infections (Large dogs >100 lbs) | 500 mg q8h IV or SC | IV/SC | q8h | — | 🌎 NA |
- CNS infections: Extrapolated from children; maximum dose per administration is 2 grams.
- Susceptible infections (Small dogs): If serum creatinine greater than 4, may be given q12h.
- Susceptible infections (Medium dogs): If serum creatinine greater than 4, may be given q12h.
- Susceptible infections (Large dogs >100 lbs): If serum creatinine greater than 4, may be given q12h.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Bacteremia/sepsis | 24 mg/kg IV q24h (once daily) or 12 mg/kg SC q8h | IV/SC | q24h or q8h | — | 🌎 NA |
| UTI | 12 mg/kg SC q12h | SC | q12h | — | 🌎 NA |
| CNS infections | 40 mg/kg IV or SC q8h | IV/SC | q8h | — | 🌎 NA |
| Systemic infections | 12 mg/kg q8h SC or 24 mg/kg IV q24h (once daily) | SC/IV | q8h or q24h | — | 🌎 NA |
| Urinary tract infections | 12 mg/kg q12h SC | SC | q12h | — | 🌎 NA |
| Susceptible infections | 125 mg (total dose) q8h IV or SC | IV/SC | q8h | — | 🌎 NA |
| Susceptible infections | 8 mg/kg IV or SC q8h | IV/SC | q8h | — | 🌎 NA |
- CNS infections: Extrapolated from children; maximum dose per administration is 2 grams.
- Susceptible infections: If serum creatinine greater than 4, may be given q12h.
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Pharmacokinetic data | IM injection | IM | — | — | 🌎 NA |
- Pharmacokinetic data: Rapidly absorbed, bioavailability equal to IV dosing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Meropenem is a broad-spectrum, synthetic carbapenem antibiotic structurally similar to imipenem. It is highly valued in veterinary medicine as a "big gun" antibiotic for severe, resistant infections.
Key characteristics include:
- Broad Spectrum: Highly effective against many gram-negative bacteria (especially Enterobacteriaceae) and anaerobes. It is less active against gram-positive bacteria compared to imipenem.
- Safety Profile: Unlike imipenem, meropenem does not require co-administration with cilastatin and has a significantly lower risk of inducing seizures, making it safer for patients with central nervous system (CNS) disease.
- Administration: It must be given parenterally (IV or SC). It is advantageous because it can be administered more rapidly and in smaller volumes than imipenem.
Clinical Pearl: To practice good antimicrobial stewardship, meropenem should be strictly reserved for documented resistant infections (e.g., multidrug-resistant E. coli or Pseudomonas) or when first-line options like aminoglycosides are contraindicated due to renal dysfunction.
Mechanism of action
Meropenem is a bactericidal beta-lactam antibiotic.
- It readily penetrates the bacterial cell envelope and binds to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall.
- Binding to PBPs → inhibition of bacterial cell wall synthesis → weakening of the peptidoglycan network → cell lysis and death.
- Resistance mechanism: Meropenem is highly resistant to degradation by most beta-lactamases, including penicillinases and cephalosporinases. Furthermore, it is stable against renal dehydropeptidase-I, eliminating the need for a protective enzyme inhibitor like cilastatin.
Safety & warnings
Contraindications
- Hypersensitivity to meropenem or other carbapenems
- History of anaphylaxis after receiving any beta-lactam antibiotic
Adverse effects
- Slight hair loss over SC injection sites
- Nausea (reported in humans)
- Vomiting (reported in humans)
- Diarrhea (reported in humans)
Precautions
Warnings and Precautions:
- Antimicrobial Stewardship: Use should be limited or avoided unless absolutely necessary to prevent the development of resistant bacterial strains that might infect humans.
- Hypersensitivity: Use with caution in patients with known allergies to penicillins or cephalosporins due to potential cross-reactivity.
- Pregnancy/Lactation: FDA Category B in humans (likely safe). It is considered likely safe to use during lactation.
- Renal Impairment: While safer than aminoglycosides, dosage adjustments (e.g., extending the dosing interval) may be necessary in severe renal failure (e.g., serum creatinine > 4 mg/dL).
Drug interactions
In vitro evidence of synergy against Pseudomonas aeruginosa
May increase serum concentrations and elimination half-life of meropenem
Monitoring
- Clinical efficacy (resolution of infection signs)
- Injection site monitoring (for SC administration)
Pharmacokinetics
Half-life
Absorption
After SC injection in dogs, bioavailability is 84%. In ewes, IM injection bioavailability is equal to intravenous dosing (~100%).
Distribution
Widely distributed in body tissues and fluids, including CSF and bile. In dogs, volume of distribution (Vd) is ~0.37 L/kg with ~12% protein binding. In ewes, Vd is 0.06 L/kg with ~43% protein binding. Human protein binding is very low (~2%).
Metabolism
One inactive metabolite has been identified, but the majority of the drug is not metabolized.
Elimination
Primarily eliminated via renal mechanisms (tubular secretion and glomerular filtration). In dogs, clearance is ~6.5 mL/min/kg. In humans, 70% of a dose is recovered unchanged in the urine over 12 hours.
Overdose
Overdoses of meropenem are unlikely to cause significant toxicity in patients with normal renal function.
- In human trials, massive doses (2 grams every 8 hours) failed to demonstrate any significant adverse effects.
- Management: Should an overdose occur, the drug can be discontinued or the next dose delayed by a few hours. If necessary (e.g., in severe renal failure), meropenem can be removed via hemodialysis.
Available products
Formulations
- Powder for solution for injection
Human-labeled
- Meropenem Powder for solution for Injection: 500 mg & 1 gram in 20 mL, & 30 mL vials (Merrem I.V., generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store powder at controlled room temperature (20-25°C; 69-77°F). Reconstituted with sterile water (up to 50 mg/mL): stable for 2 hours at room temperature; up to 12 hours refrigerated. Diluted in normal saline or sterile water (1-20 mg/mL): stable up to 48 hours refrigerated. For SC use in veterinary patients (diluted to 20 mg/mL in 0.9% NaCl): protect from light, stable up to 96 hours refrigerated; once brought to room temperature, use within 6 hours. Freezing is generally not recommended by the manufacturer, though some studies show stability at -20°C for 14 days with 10% potency loss.
Client information
Meropenem is a powerful antibiotic typically reserved for serious, resistant infections.
- Administration: Because of the severity of the infections it treats, your pet will usually receive this medication while hospitalized. However, for certain conditions like resistant urinary tract infections, you may be instructed to give subcutaneous (under the skin) injections at home.
- Technique: If giving injections at home, ensure you understand the proper technique. You may notice slight hair loss at the injection sites; this is generally harmless.
- Storage: Follow your veterinarian's storage instructions strictly, as reconstituted liquid meropenem has a limited shelf life and usually requires refrigeration.
- Completion: Always complete the entire course of antibiotics prescribed, even if your pet seems completely better, to prevent the bacteria from returning and becoming even more resistant.
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.