Meropenem

Meropenem is a broad-spectrum carbapenem beta-lactam used for selected serious resistant infections in veterinary patients. Its activity includes many susceptible Enterobacterales, some Pseudomonas isolates and anaerobes. It retains activity against some organisms producing extended-spectrum beta-lactamases. Veterinary clinical use centers on organism-directed treatment of difficult systemic or deep infections.

Group

Carbapenem antibacterial

Mechanism of Action

Meropenem binds bacterial penicillin-binding proteins and inhibits peptidoglycan synthesis and cross-linking. Loss of normal cell-wall integrity causes lysis of susceptible growing bacteria. Stability against many beta-lactamases contributes to its spectrum, while carbapenemases, altered permeability and other resistance mechanisms can abolish activity. Relative stability to renal dehydropeptidase permits use without a cilastatin partner.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Resistant Enterobacterales infection	10 mg/kg	IV, IM, SC	Every 8 h	Susceptibility-directed use. IM/SC use is extralabel.
Pseudomonas infection	30 mg/kg	IV, IM, SC	Every 8 h	Susceptibility-directed use. IM/SC use is extralabel.
Continuous-infusion antibacterial therapy — Loading	1 mg/kg	IV	Once	Follow with the separately listed infusion; solution stability and line compatibility require an appropriate hospital protocol.
Continuous-infusion antibacterial therapy — Maintenance	1 mg/kg/hour	IV	Continuous	Use after the separately listed loading dose; prepare and replace infusion solutions within validated stability limits.
Bacteremia or sepsis	24 mg/kg	IV	Every 24 h	A distinct historical formulary alternative; susceptibility and time-dependent exposure must guide selection.
Bacteremia or sepsis	12 mg/kg	SC	Every 8 h
Urinary tract infection	12 mg/kg	SC	Every 12 h
Central nervous system infection	40 mg/kg	IV, SC	Every 8 h	Maximum 2000 mg/dose; Extrapolated from pediatric treatment; reserve for essential susceptibility-confirmed use. Maximum 2 g per administration.
Historical size-based systemic regimen	Reference only	IV		Historical totals every 8 hours: 125 mg for small dogs, 250 mg for medium dogs and 500 mg for dogs >100 lb; first two size definitions are absent. SC was also listed. A 12-hour interval was suggested with serum creatinine >4, but the unit is unstated; clarify before use.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Susceptible resistant bacterial infection	10 mg/kg	IV, IM, SC	Every 12 h	IM/SC use is extralabel; choose therapy with culture results.
Bacteremia or sepsis	24 mg/kg	IV	Every 24 h	A distinct historical formulary alternative; susceptibility and time-dependent exposure must guide selection.
Bacteremia or sepsis	12 mg/kg	SC	Every 8 h
Urinary tract infection	12 mg/kg	SC	Every 12 h
Central nervous system infection	40 mg/kg	IV, SC	Every 8 h	Maximum 2000 mg/dose; Extrapolated from pediatric treatment; reserve for essential susceptibility-confirmed use. Maximum 2 g per administration.
Alternative systemic infection regimen	8 mg/kg	IV, SC	Every 8 h
Historical fixed systemic regimen	Reference only	SC		125 mg total every 8 hours by IV or SC was listed for cats and small dogs, without individual weight qualification. The weight-based cat alternatives are more explicit; do not extrapolate across body sizes.

Indications

Treatment of serious meropenem-susceptible resistant Enterobacterales infections, including selected sepsis, urinary or deep soft-tissue infections.
Treatment of selected susceptible Pseudomonas infections resistant to suitable alternative agents.
Specialist treatment of susceptible central nervous system or mixed aerobic–anaerobic infections when meropenem provides appropriate organism-directed coverage.

Contraindications

Serious carbapenem hypersensitivity
Prior anaphylaxis to a beta-lactam antibiotic

Interactions

Do not mix in a syringe or vial with other antibiotics.
Carbapenems can substantially lower valproate exposure.
Probenecid can increase meropenem concentrations and elimination half-life.

Adverse effects

Hypersensitivity
Local injection-site hair changes
Gastrointestinal disturbance
Possible neurologic effects with excessive exposure

Toxicity

Discontinue for serious hypersensitivity or neurologic toxicity. Impaired renal clearance can increase exposure.

Preparations

Preparation	Form	Strength	Route
Meronic 500 mg injection vial Dry meropenem vial. Calculate vial equivalents only until this product’s final concentration is confirmed; no assumed injection volume.	Injection	500 mg / vial	IV
Meronic 1000 mg injection vial Dry meropenem vial. Calculate vial equivalents only until this product’s final concentration is confirmed; no assumed injection volume.	Injection	1000 mg / vial	IV
Meropenem compounded saline solution 20 mg/mL for SC use Sterile saline formulation described for veterinary SC administration. Product-specific compounding, light protection and validated storage are required; do not use Meronic vial size alone to infer this concentration.	Injection	20 mg / mL	SC

Monitoring and Administration

Confirm culture and susceptibility before selecting this reserve antimicrobial and reassess for de-escalation. Veterinary doses are supported primarily by pharmacokinetics.

Use validated product-specific diluent and storage times. Published formulation information describes 50 mg/mL reconstitution, room-temperature solution stability of 12 hours and refrigerated stability of 3 days; do not transfer these times across different manufacturers, diluents or concentrations without confirmation.

Inspect for particulates and marked amber/brown discoloration; slight yellowing alone need not indicate loss of potency.

Meropenem storage periods vary substantially by product and diluent. One manufacturer-based description limits reconstituted stock up to 50 mg/mL to 2 hours at room temperature or 12 hours refrigerated; selected 1–20 mg/mL saline/water syringe dilutions to 48 hours refrigerated. A reported 20 mg/mL saline SC preparation had a 96-hour refrigerated period and 6 hours after warming; these are formulation-specific and cannot replace the actual product instruction.

Prepare reserve-antibiotic therapy using renal function, organism MIC and infection site; do not automatically substitute the once-daily IV historical course for more frequent modern regimens.