Meropenem

Carbapenem antibiotic Beta-lactam antibiotic

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV 8.5 mg/kg (or 10-20 mg/kg in severe cases) q8h Duration: Varies; typically 7-14 days depending on infection
Notes: Administer slowly over 15-30 minutes. Adjust dose in renal impairment.
Cat IV 8.5 mg/kg (or 10-20 mg/kg in severe cases) q8h Duration: Varies; typically 7-14 days
Notes: Administer slowly. Adjust dose in renal impairment.
Horse IV 10-20 mg/kg q8h Duration: Varies; often 5-10 days
Notes: For neonatal septicemia, use higher end. Monitor renal function.
Cattle IV 10 mg/kg q8h Duration: Varies; short-term use
Notes: Extra-label use only; observe withdrawal times.
Small Ruminants IV 10 mg/kg q8h Duration: Varies
Notes: Extra-label use; limited data.
Rabbit IV 10-20 mg/kg q8h Duration: Varies
Notes: Use cautiously; limited data.

Clinical Indications & Species Uses

General Indications
  • Reserved for severe, life-threatening infections, especially those caused by multidrug-resistant Gram-negative bacteria, or when other antibiotics have failed.
Dog (Canine)
  • Treatment of serious infections caused by susceptible bacteria, including complicated urinary tract infections, pneumonia, septicemia, intra-abdominal infections, and skin/soft tissue infections. Often reserved for multidrug-resistant infections.
Cat (Feline)
  • Similar to dogs: serious infections, including complicated UTIs, respiratory infections, septicemia, and infections caused by multidrug-resistant organisms.
Horse (Equine)
  • Treatment of severe infections such as neonatal septicemia, pneumonia, and peritonitis, especially when caused by resistant bacteria.
Exotic & Other Species
  • May be used in exotic animals (e.g., reptiles, small mammals) for severe infections, but dosing is often extrapolated.

Pharmacology & Mechanism of Action

Drug Class: Carbapenem antibiotic | Pharmacological Group: Beta-lactam antibiotic

Mechanism of Action: Meropenem exerts its bactericidal action by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) located in the bacterial cell wall, leading to inhibition of peptidoglycan cross-linking, activation of autolytic enzymes, and ultimately cell lysis. Its broad-spectrum activity is due to its high affinity for multiple PBPs and its stability against most beta-lactamases, including extended-spectrum beta-lactamases (ESBLs) and AmpC cephalosporinases, but not carbapenemases.

Pharmacodynamics: Meropenem is a time-dependent bactericidal antibiotic. Its efficacy correlates with the percentage of time that the free drug concentration exceeds the minimum inhibitory concentration (MIC) of the pathogen. It exhibits a post-antibiotic effect against Gram-negative bacteria but minimal against Gram-positive organisms. It is highly active against a wide range of aerobic and anaerobic bacteria, including many multidrug-resistant strains.

⚡ Pharmacokinetics Summary

Absorption: Meropenem is not absorbed orally and must be administered parenterally. After intravenous administration, it achieves high plasma concentrations rapidly.
Distribution: Meropenem distributes widely into tissues and fluids, including cerebrospinal fluid (especially when meninges are inflamed), lung, kidney, bile, and peritoneal fluid. It has a volume of distribution of approximately 0.3 L/kg in dogs and cats. Protein binding is low (approximately 2% in humans, similar in animals).
Metabolism: Meropenem is metabolized primarily by hydrolysis of the beta-lactam ring to an inactive metabolite. In humans, about 70% is excreted unchanged in the urine, with the remainder as the open-ring metabolite. Similar metabolism is expected in animals.
Excretion: Meropenem is primarily excreted renally via glomerular filtration and tubular secretion. In animals with normal renal function, the elimination half-life is short (approximately 1 hour in dogs and cats). Dosage adjustment is necessary in animals with renal impairment.
Half-Life: Dogs: ~0.7-1 hour; Cats: ~0.8-1 hour; Horses: ~0.5-1 hour; Cattle: ~0.5-1 hour (estimated).
Bioavailability: Not orally bioavailable; must be given IV or IM (IM not recommended due to pain).
Protein Binding: Approximately 2% in humans; low in animals.

Available Formulations & Strengths

Injectable Powder for Reconstitution 500 mg/vial, 1 g/vial (IV)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to meropenem or other beta-lactam antibiotics (e.g., penicillins, cephalosporins).
  • Use in patients with a history of anaphylactic reactions to beta-lactams.
  • Do not use in animals with known carbapenem allergy.
Warnings & Clinical Precautions:
  • Use with caution in animals with renal impairment; dose adjustment may be necessary.
  • May cause seizures, especially in animals with CNS disorders or renal impairment.
  • Use only for severe infections where benefits outweigh risks due to its broad-spectrum activity and potential for promoting resistance.
  • In food animals, extra-label use is prohibited in some countries; check regulations.
  • Administer slowly IV to reduce the risk of infusion-related reactions.

Adverse Effects & Reactions

Common:

  • Injection site pain or phlebitis
  • Nausea or vomiting (rare in animals)
  • Diarrhea

Serious / Severe:

  • Seizures
  • Anaphylaxis
  • Clostridioides difficile-associated diarrhea
  • Bone marrow suppression (rare)

Rare:

  • Hepatotoxicity
  • Nephrotoxicity
  • Eosinophilia
  • Thrombocytosis

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Probenecid Probenecid competes for tubular secretion, increasing meropenem plasma concentrations and half-life. Moderate
Valproic acid Meropenem may reduce valproic acid concentrations, leading to loss of seizure control. High
Nephrotoxic drugs (e.g., aminoglycosides, NSAIDs) Increased risk of nephrotoxicity when used concurrently. Moderate
Warfarin May enhance anticoagulant effect; monitor coagulation parameters. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Seizures
  • Neurological signs
  • Gastrointestinal upset
  • Renal impairment

Emergency Treatment Protocol: Treatment is symptomatic and supportive. There is no specific antidote. In cases of overdose, discontinue the drug, provide supportive care, and consider hemodialysis in severe cases (meropenem is dialyzable). Monitor renal function and neurological status.

Food Animal Withdrawal Times

Not approved for food animals. Extra-label use in food animals is prohibited in many countries. If used, extended withdrawal periods must be considered; consult regulatory authorities. No established withdrawal times.

Storage, Handling & Regulatory Information

Storage Temperature: Store powder at controlled room temperature 20-25°C (68-77°F).

Handling & Special Conditions: Reconstituted solutions are stable for up to 8 hours at room temperature or 24 hours under refrigeration (2-8°C). Do not freeze.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use in the US. Approved for human use; used extra-label in veterinary medicine.

Extra-Label (Off-Label) Use: In the US, extra-label use in animals is permitted under AMDUCA for non-food animals. For food animals, extra-label use is prohibited if an approved animal drug exists that is labeled for the indication and is effective. In the EU, similar restrictions apply. Use in food animals is generally discouraged.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Meropenem is a potent carbapenem antibiotic reserved for severe infections, particularly those caused by multidrug-resistant Gram-negative bacteria. It is not absorbed orally and must be given IV. Due to its broad-spectrum activity, it should be used judiciously to minimize the development of resistance. In veterinary practice, it is often used in critical care settings for septicemia, pneumonia, and complicated infections. Dosing is typically based on extrapolation from human data and limited veterinary pharmacokinetic studies. Renal function should be monitored, and dose adjustments made in animals with renal impairment. Because of its short half-life, frequent dosing (q8h) is required. Use in food animals is highly restricted due to lack of withdrawal data and public health concerns. Always perform culture and sensitivity testing when possible to ensure appropriate use.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)