Meropenem
Meropenem is a parenteral, bactericidal carbapenem used as a last-resort option for documented multidrug-resistant bacterial infections in dogs and cats when suitable alternatives are unavailable. Culture, organism identification and a measured MIC are important because resistance and exposure requirements vary.
Veterinary treatment is extra-label and supported mainly by pharmacokinetic evidence rather than controlled clinical efficacy trials. Renal function influences clearance; assess renal indices and individualize dosing in renal impairment. No food-animal withdrawal interval is established.
Group
Carbapenem beta-lactam antibacterial.
Mechanism of Action
Binding to bacterial penicillin-binding proteins interrupts peptidoglycan cross-linking and cell-wall synthesis, producing bacterial lysis. Activity depends principally on the time that unbound concentrations remain above the organism’s MIC.
The spectrum includes susceptible aerobic and anaerobic organisms, including some ESBL-producing Enterobacterales and Pseudomonas aeruginosa. Carbapenem resistance can defeat treatment. Methicillin-resistant staphylococci are resistant; enterococcal activity is variable and cannot be assumed.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible Enterobacterales infection — Maintenance | 10 mg/kg | IV, SC | Every 8 h | Older formulary regimen for low-MIC isolates. Do not assume adequate exposure at an MIC of 1 mcg/mL; newer canine modelling supports the separate higher-exposure alternatives. Individualize for renal impairment. |
| Susceptible Enterobacterales infection — Maintenance | 10 mg/kg | IM | Every 8 h | Older formulary regimen for low-MIC isolates. Do not assume adequate exposure at an MIC of 1 mcg/mL; newer canine modelling supports the separate higher-exposure alternatives. Individualize for renal impairment. Canine intramuscular evidence is limited. |
| Susceptible Pseudomonas aeruginosa infection — Maintenance | 30 mg/kg | IV, SC | Every 8 h | Older formulary regimen; do not assume adequate exposure at an MIC of 2 mcg/mL. The separate intensified intravenous regimen addresses that target. Individualize for renal impairment. |
| Susceptible Pseudomonas aeruginosa infection — Maintenance | 30 mg/kg | IM | Every 8 h | Older formulary regimen; do not assume adequate exposure at an MIC of 2 mcg/mL. The separate intensified intravenous regimen addresses that target. Individualize for renal impairment. Canine intramuscular evidence is limited. |
| Susceptible bacterial infection by continuous infusion — Loading | 1 mg/kg | IV | Once | Precedes the continuous infusion maintenance record for this use. Individualize for renal impairment. |
| Susceptible bacterial infection by continuous infusion — Maintenance | 1 mg/kg/hour | IV | Continuous | Follows the loading record for this use. Pharmacy preparation, solution stability and replacement frequency require a validated infusion plan; this rate does not define a bag concentration or hang time. Individualize for renal impairment. |
| Susceptible Enterobacterales infection — Maintenance | 20–30 mg/kg | IV | Every 8 h | Alternative higher-exposure regimen from canine PK/PD modelling for isolates with MIC ≤1 mcg/mL; not a clinical efficacy trial. Individualize for renal impairment. |
| Susceptible Enterobacterales infection — Maintenance | 10 mg/kg | IV | Every 6 h | Alternative higher-exposure regimen from canine PK/PD modelling for isolates with MIC ≤1 mcg/mL; not additive to other schedules for this use. Individualize for renal impairment. |
| Susceptible Pseudomonas aeruginosa infection — Maintenance | 20–30 mg/kg | IV | Every 6 h | Intensified regimen from canine PK/PD modelling for isolates with MIC ≤2 mcg/mL; not a clinical efficacy trial or an extension to other routes. Individualize for renal impairment. |
Cat
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible multidrug-resistant bacterial infection — Maintenance | 10 mg/kg | IV, IM, SC | Every 12 h | Supported by a small healthy-cat pharmacokinetic study; efficacy predictions depend on the isolate MIC and may not apply unchanged to critically ill cats. Individualize for renal impairment. |
Indications
- Culture-confirmed multidrug-resistant Enterobacterales infections, including susceptible Escherichia coli and Klebsiella pneumoniae.
- Susceptible Pseudomonas aeruginosa infections when other effective antibacterial options are unsuitable.
- Severe susceptible mixed aerobic–anaerobic infections requiring a reserve parenteral antibacterial.
Contraindications
- Known hypersensitivity to meropenem, another carbapenem or formulation components.
- Previous severe immediate or severe cutaneous hypersensitivity to another beta-lactam antibiotic.
- Renal impairment requires an individualized regimen rather than automatic use of the schedules below; it is not an absolute contraindication.
- Use cautiously with pre-existing seizure disorders. Safety during pregnancy and lactation in dogs and cats is insufficiently established.
Interactions
- Probenecid reduces renal elimination and increases meropenem exposure; concurrent use is generally avoided.
- Valproic acid or divalproex concentrations can fall markedly, with loss of seizure control; avoid concurrent treatment where possible.
- Do not mix with other antibiotics or other medicines in the same vial, syringe or infusion solution without demonstrated compatibility.
Adverse effects
- Injection-site discomfort or inflammation; mild local hair changes or alopecia may follow subcutaneous administration in cats.
- Hypersensitivity reactions, including anaphylaxis.
- Gastrointestinal upset, including vomiting or diarrhoea.
- Seizures or other CNS effects are possible, especially with renal accumulation or pre-existing CNS disease.
- Human reports include severe skin reactions, liver-enzyme abnormalities, blood-cell changes and rhabdomyolysis; their frequency in veterinary patients is not established.
Toxicity
Accumulation, particularly with impaired renal clearance, can increase neurologic toxicity. Stop administration if seizures or a serious hypersensitivity reaction develops and provide supportive treatment. No specific antidote or validated toxic-dose threshold for dogs or cats is established. Assess renal function and monitor clinical response during prolonged treatment.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Meronem IV 500 mg vial (reconstituted 50 mg/mL) Dry powder containing 500 mg meropenem equivalent as trihydrate; the stated concentration applies only after reconstitution with sterile water for injection to approximately 10 mL. Further dilution changes the concentration. Bolus solution: up to 3 hours at ≤25°C or 12 hours at 2–8°C. Prefer immediate use; do not freeze. Product labelling supports intravenous use; veterinary intramuscular and subcutaneous regimens are extra-label. | Injection | 50 mg / mL | IV |
| Meronem IV 1 g vial (reconstituted 50 mg/mL) Dry powder containing 1000 mg meropenem equivalent as trihydrate; the stated concentration applies only after reconstitution with sterile water for injection to approximately 20 mL. Further dilution changes the concentration. Bolus solution: up to 3 hours at ≤25°C or 12 hours at 2–8°C. Prefer immediate use; do not freeze. Product labelling supports intravenous use; veterinary intramuscular and subcutaneous regimens are extra-label. | Injection | 50 mg / mL | IV |
| MERREM IV 500 mg vial (reconstituted 50 mg/mL) Dry powder containing 500 mg meropenem equivalent as trihydrate; the stated concentration applies only after reconstitution with sterile water for injection to approximately 10 mL. Further dilution changes the concentration. Bolus solution: up to 3 hours at ≤25°C or 13 hours at ≤5°C. Prefer immediate use; do not freeze. Product labelling supports intravenous use; veterinary intramuscular and subcutaneous regimens are extra-label. | Injection | 50 mg / mL | IV |
| MERREM IV 1 g vial (reconstituted 50 mg/mL) Dry powder containing 1000 mg meropenem equivalent as trihydrate; the stated concentration applies only after reconstitution with sterile water for injection to approximately 20 mL. Further dilution changes the concentration. Bolus solution: up to 3 hours at ≤25°C or 13 hours at ≤5°C. Prefer immediate use; do not freeze. Product labelling supports intravenous use; veterinary intramuscular and subcutaneous regimens are extra-label. | Injection | 50 mg / mL | IV |
