Marbofloxacin (Zeniquin)

Fluoroquinolone antibiotic Antibacterial

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 2.75-5.5 mg/kg q24h Duration: 5-7 days for UTIs; 10-14 days for skin infections; up to 28 days for deep pyoderma or osteomyelitis
Notes: Administer with or without food; adjust dose for renal impairment.
Cat PO 2.75-5.5 mg/kg q24h Duration: 5-7 days for UTIs; 10-14 days for skin/respiratory infections
Notes: Use lower end of dose for cats with renal insufficiency.
Horse IV 2 mg/kg q24h Duration: 5-10 days
Notes: Off-label use; not approved in horses intended for human consumption.
Horse PO 2-4 mg/kg q24h Duration: 5-10 days
Notes: Oral bioavailability is lower; use higher end of dose.
Cattle IM 2 mg/kg q24h Duration: 3-5 days
Notes: Extra-label use only; not approved in many countries; observe withdrawal times.
Rabbit PO 5-10 mg/kg q24h Duration: 5-14 days
Notes: Off-label; use cautiously due to potential GI dysbiosis.
Bird (companion) PO 10-20 mg/kg q24h Duration: 5-10 days
Notes: Off-label; adjust based on species and sensitivity.

Clinical Indications & Species Uses

General Indications
  • Treatment of infections caused by susceptible Gram-positive and Gram-negative bacteria, including those resistant to other antibiotic classes.
Dog (Canine)
  • Skin and soft tissue infections (e.g., pyoderma, wounds)
  • Urinary tract infections (UTIs)
  • Respiratory tract infections (e.g., pneumonia, bronchitis)
  • Prostatitis
  • Bone and joint infections (osteomyelitis)
  • Bacterial enteritis
Cat (Feline)
  • Skin and soft tissue infections
  • Urinary tract infections (including pyelonephritis)
  • Respiratory tract infections (e.g., feline upper respiratory disease complex)
  • Abscesses and wound infections
Horse (Equine)
  • Respiratory tract infections (e.g., pneumonia, pleuropneumonia)
  • Urinary tract infections
  • Skin and soft tissue infections
  • Septic arthritis and osteomyelitis (off-label use)
Exotic & Other Species
  • Reptiles: off-label use for bacterial infections; small mammals (ferrets, guinea pigs): off-label use for respiratory and urinary infections.

Pharmacology & Mechanism of Action

Drug Class: Fluoroquinolone antibiotic | Pharmacological Group: Antibacterial

Mechanism of Action: Marbofloxacin is a bactericidal fluoroquinolone that inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes essential for DNA replication, transcription, repair, and recombination. By binding to these enzymes, it prevents the supercoiling of bacterial DNA, leading to rapid bacterial cell death. It is active against both Gram-positive and Gram-negative bacteria, as well as some mycoplasmas and rickettsiae.

Pharmacodynamics: Marbofloxacin exhibits concentration-dependent bactericidal activity. The ratio of peak plasma concentration (Cmax) to minimum inhibitory concentration (MIC) and the area under the curve (AUC) to MIC ratio are key predictors of efficacy. It has a post-antibiotic effect (PAE) against susceptible organisms, allowing for once-daily dosing. It is effective against many pathogens including E. coli, Pasteurella spp., Staphylococcus spp., and Mycoplasma spp.

⚡ Pharmacokinetics Summary

Absorption: Marbofloxacin is well absorbed after oral administration in dogs and cats, with bioavailability approaching 100%. Absorption is slightly delayed by food but not significantly reduced.
Distribution: It is widely distributed in tissues and body fluids, with high concentrations in skin, lung, kidney, prostate, and bone. It penetrates well into cells and achieves concentrations in macrophages and polymorphonuclear leukocytes. Volume of distribution is large (1.1-1.4 L/kg in dogs).
Metabolism: Marbofloxacin is minimally metabolized in the liver; the majority of the drug is excreted unchanged in the urine. Some metabolites (N-desmethyl-marbofloxacin and N-oxide-marbofloxacin) have been identified but are of minor importance.
Excretion: Excretion is primarily renal (about 40-50% in dogs and cats) and also via the biliary/fecal route. In dogs, approximately 40% is excreted in urine and 60% in feces. In cats, similar proportions are observed.
Half-Life: Dogs: 10-14 hours; Cats: 10-12 hours; Horses: 6-8 hours; Cattle: 4-6 hours (but not approved for food animals in many countries).
Bioavailability: Oral bioavailability is nearly 100% in dogs and cats; in horses, oral bioavailability is about 60-70%.
Protein Binding: Low protein binding: approximately 10% in dogs and cats.

Available Formulations & Strengths

Oral Tablet 25 mg, 50 mg, 100 mg, 200 mg (PO)
Injectable Solution (for veterinary use in some countries) 10% (100 mg/mL) (IV, IM, SC)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to marbofloxacin or other fluoroquinolones
  • Known or suspected allergy to quinolones
  • Use in growing animals (dogs <8 months of age, cats <12 months of age) due to risk of arthropathy
  • Use in pregnant or lactating animals unless benefits outweigh risks (safety not established)
  • Use in animals with known CNS disorders (e.g., epilepsy) as it may lower seizure threshold
  • Concurrent use with theophylline or other xanthines (may increase risk of CNS stimulation)
Warnings & Clinical Precautions:
  • Use with caution in animals with renal or hepatic impairment; dose adjustment may be necessary.
  • Fluoroquinolones can cause cartilage erosion in young, growing animals; avoid in immature animals.
  • May cause CNS stimulation (seizures) in predisposed animals; use with caution in animals with a history of seizures.
  • In cats, high doses may cause retinal toxicity; monitor for visual changes.
  • Use in horses: not approved for food animals; must observe withdrawal times.
  • Extra-label use in food animals requires a valid veterinary-client-patient relationship and observance of extended withdrawal times.
  • May cause photosensitivity; avoid excessive sunlight exposure during treatment.
  • Do not use concurrently with antacids containing magnesium, aluminum, or calcium, or with sucralfate, as they reduce absorption.
  • Use with caution in animals with myasthenia gravis (may exacerbate muscle weakness).

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (vomiting, diarrhea, anorexia)
  • Lethargy
  • Restlessness

Serious / Severe:

  • Cartilage damage in young animals
  • CNS signs (seizures, ataxia, agitation)
  • Retinal degeneration in cats (high doses)
  • Acute renal failure (rare)
  • Hepatotoxicity (rare)

Rare:

  • Allergic reactions (urticaria, anaphylaxis)
  • Blood dyscrasias (leukopenia, thrombocytopenia)
  • Tendon rupture (rare in animals)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Antacids (aluminum, magnesium, calcium) Decreased absorption of marbofloxacin due to chelation; administer at least 2 hours apart. Moderate
Sucralfate Reduced absorption of marbofloxacin; separate administration by at least 2 hours. Moderate
Theophylline Increased plasma levels of theophylline, leading to potential toxicity (CNS stimulation, seizures). High
Warfarin Potential increased anticoagulant effect; monitor coagulation parameters. Moderate
Nonsteroidal anti-inflammatory drugs (NSAIDs) Increased risk of CNS stimulation and seizures; use with caution. Moderate
Corticosteroids Increased risk of tendon rupture (rare in animals); monitor. Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • CNS signs (depression, tremors, seizures)
  • Ataxia
  • Anorexia
  • In cats: mydriasis, retinal degeneration with chronic high doses

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce emesis if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide fluid therapy to maintain hydration and promote excretion. Control seizures with diazepam or barbiturates. Monitor renal and hepatic function. In severe cases, consider hemodialysis (though efficacy is uncertain).

Food Animal Withdrawal Times

🥩 Meat: 5 days🥛 Milk: 4 days

Withdrawal times are not established for marbofloxacin in many countries; extra-label use in food animals requires extended withdrawal periods (e.g., 28 days for meat and 7 days for milk in the US). Consult regulatory guidelines.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), excursions permitted between 15-30°C (59-86°F).

Handling & Special Conditions: Protect from moisture. Keep in tightly closed container. Do not use if tablets are discolored or show signs of deterioration.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved by FDA for use in dogs and cats (Zeniquin). Not approved for food animals.

Extra-Label (Off-Label) Use: In the US, marbofloxacin is approved for use in dogs and cats. Extra-label use in other species is permitted under AMDUCA (Animal Medicinal Drug Use Clarification Act) with a valid veterinary-client-patient relationship, but requires extended withdrawal times for food animals. In the EU, use in food-producing animals is prohibited or restricted.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Marbofloxacin is a broad-spectrum fluoroquinolone with excellent tissue penetration and a long half-life, allowing once-daily dosing. It is particularly useful for skin, urinary, and respiratory infections in dogs and cats. Due to its potential to cause arthropathy in young animals, it should be avoided in growing animals. It is contraindicated in animals with known hypersensitivity to fluoroquinolones. Use with caution in animals with renal impairment, as dose adjustment may be needed. In food animals, extra-label use is restricted and withdrawal times must be observed. Monitor for adverse effects, especially CNS signs and GI upset. Always culture and sensitivity testing when possible to ensure appropriate use and reduce antimicrobial resistance.

References & Literature

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