Enrofloxacin

Fluoroquinolone antibiotic Antibacterial

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO, IV, IM, SC 2.5-5 mg/kg (up to 10 mg/kg for severe infections) q12h or q24h (once daily for most infections) Duration: 5-14 days; for pyoderma, may require 3-4 weeks or longer
Notes: For urinary tract infections, lower doses may be effective. For Pseudomonas infections, higher doses (10 mg/kg) may be needed.
Cat PO, IV, IM, SC 2.5-5 mg/kg q12h or q24h Duration: 5-14 days
Notes: Cats may be more prone to ocular toxicity at high doses; avoid doses >5 mg/kg for prolonged periods.
Horse PO, IV 5-7.5 mg/kg q24h Duration: 5-14 days
Notes: Oral absorption is variable; IV is preferred for severe infections. Use with caution in young foals due to cartilage effects.
Cattle SC, IM, IV 7.5-12.5 mg/kg q24h (single dose for BRD in some formulations) Duration: 3-5 days
Notes: For BRD, a single subcutaneous dose of 7.5-12.5 mg/kg is approved in some countries. Withdrawal times must be observed.
Small Ruminants (sheep, goats) PO, SC, IM 5-10 mg/kg q24h Duration: 3-5 days
Notes: Extra-label use; observe withdrawal times.
Rabbit PO, SC 5-10 mg/kg q12h or q24h Duration: 7-14 days
Notes: Oral solution or tablets may be used; ensure adequate hydration.
Birds/Poultry PO (in water), IM 10-15 mg/kg (PO) or 10 mg/kg (IM) q12h or q24h Duration: 3-7 days
Notes: For water medication, adjust dose based on water consumption. Not approved for poultry in some countries due to resistance concerns.
Reptiles IM, PO 5-10 mg/kg q24-48h Duration: 7-14 days
Notes: Dosing intervals may be longer due to slower metabolism.

Clinical Indications & Species Uses

General Indications
  • Treatment of infections caused by susceptible Gram-negative and Gram-positive bacteria, and Mycoplasma
Dog (Canine)
  • Urinary tract infections
  • Skin and soft tissue infections
  • Respiratory tract infections
  • Prostatitis
  • Pyoderma (deep and superficial)
  • Wound infections
  • Bacterial gastroenteritis
  • Otitis externa (systemic therapy)
Cat (Feline)
  • Urinary tract infections
  • Skin and soft tissue infections
  • Respiratory tract infections
  • Abscesses
  • Wound infections
  • Bacterial gastroenteritis
  • Chlamydophila felis infections
Horse (Equine)
  • Respiratory tract infections (e.g., pneumonia, pleuropneumonia)
  • Urinary tract infections
  • Skin and soft tissue infections
  • Septicemia (in foals)
  • Reproductive tract infections
Cattle (Bovine)
  • Bovine respiratory disease (BRD) complex
  • Pneumonia
  • Metritis
  • Mastitis (off-label)
  • Foot rot
  • Septicemia
Small Ruminants (Sheep / Goat)
  • Respiratory tract infections
  • Enteritis
  • Mastitis (off-label)
  • Metritis
  • Foot rot
Rabbit & Small Mammals
  • Respiratory tract infections (e.g., Pasteurella multocida)
  • Urinary tract infections
  • Abscesses
  • Skin infections
Avian & Poultry
  • Respiratory tract infections (e.g., Mycoplasma, E. coli)
  • Enteritis
  • Septicemia
  • Colibacillosis
  • Salmonellosis
Exotic & Other Species
  • Reptiles: respiratory infections, abscesses; Small mammals (ferrets, guinea pigs): respiratory and urinary infections; Fish: systemic bacterial infections (off-label)

Pharmacology & Mechanism of Action

Drug Class: Fluoroquinolone antibiotic | Pharmacological Group: Antibacterial

Mechanism of Action: Enrofloxacin 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, including many that are resistant to other antibiotic classes.

Pharmacodynamics: Enrofloxacin 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 are important predictors of efficacy. It has a post-antibiotic effect (PAE) against susceptible organisms, allowing for once-daily dosing in many species. It is particularly effective against Enterobacteriaceae, Pasteurella, Mycoplasma, and some Pseudomonas species.

⚡ Pharmacokinetics Summary

Absorption: Enrofloxacin is well absorbed after oral administration in most species, with bioavailability ranging from 60-100% in dogs and cats. It is also absorbed after intramuscular and subcutaneous injection. Food can delay absorption but not the extent.
Distribution: Enrofloxacin is widely distributed throughout the body, achieving high concentrations in tissues, including lung, liver, kidney, skin, bone, and prostate. It penetrates well into cells and body fluids, including cerebrospinal fluid (though lower than serum), synovial fluid, and bronchial secretions. It crosses the placenta and is excreted in milk.
Metabolism: Enrofloxacin is partially metabolized in the liver to ciprofloxacin, which is also an active metabolite. The extent of metabolism varies by species; in dogs and cats, approximately 10-20% is converted to ciprofloxacin, while in other species it may be higher.
Excretion: Enrofloxacin and its metabolites are primarily excreted via the kidneys (glomerular filtration and tubular secretion) and also via the biliary route. In some species, fecal excretion is significant. Renal impairment may require dose adjustment.
Half-Life: Dogs: 4-6 hours; Cats: 4-6 hours; Horses: 4-9 hours; Cattle: 2-3 hours; Pigs: 6-8 hours; Rabbits: 1-2 hours; Birds: 2-4 hours (varies by species).
Bioavailability: Oral: 60-100% in dogs and cats; IM/SC: nearly 100% in most species.
Protein Binding: Enrofloxacin is approximately 20-50% protein-bound in plasma, depending on species.

Available Formulations & Strengths

Oral Tablet 22.7 mg, 68 mg, 136 mg (PO)
Oral Solution 50 mg/mL, 100 mg/mL (PO)
Injectable Solution 50 mg/mL, 100 mg/mL (IV, IM, SC)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to fluoroquinolones
  • Known or suspected cases of epilepsy or seizure disorders (may lower seizure threshold)
  • Young, growing animals (especially dogs and horses) due to risk of arthropathy
  • Pregnancy and lactation (unless benefits outweigh risks, as it may affect fetal cartilage development)
  • Use in cats with known retinal degeneration
  • Concurrent use with theophylline (may increase theophylline levels)
Warnings & Clinical Precautions:
  • Use with caution in animals with renal or hepatic impairment; dose adjustment may be necessary.
  • In young animals (e.g., puppies, kittens, foals), avoid use or use with extreme caution due to potential cartilage damage.
  • In cats, high doses or prolonged therapy may cause retinal degeneration; monitor for vision changes.
  • May cause crystalluria in alkaline urine; ensure adequate hydration.
  • Fluoroquinolones may cause CNS stimulation; use with caution in animals with a history of seizures.
  • In food animals, observe withdrawal times to avoid violative residues.
  • Use in poultry is prohibited in some countries due to public health concerns about resistance.
  • Do not administer orally with antacids containing magnesium, aluminum, or calcium, as they chelate and reduce absorption.

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (vomiting, diarrhea, anorexia)
  • Injection site reactions (pain, swelling)
  • Excessive salivation (especially in cats after oral administration)

Serious / Severe:

  • Cartilage erosion in young animals
  • Retinal degeneration in cats (especially at high doses)
  • Seizures (especially in animals with predisposing factors)
  • Acute renal failure (rare)
  • Hepatotoxicity (rare)

Rare:

  • Blood dyscrasias (leukopenia, thrombocytopenia)
  • Allergic reactions (anaphylaxis, skin rash)
  • Tendon rupture (reported in humans, rare in animals)
  • Photosensitivity

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Antacids (aluminum, magnesium, calcium) Reduced absorption of enrofloxacin due to chelation Moderate
Sucralfate Reduced absorption of enrofloxacin Moderate
Theophylline Increased theophylline levels, risk of toxicity High
Warfarin Increased anticoagulant effect Moderate
Nonsteroidal anti-inflammatory drugs (NSAIDs) Increased risk of CNS stimulation and seizures High
Corticosteroids Increased risk of tendon damage Moderate
Nitrofurantoin Antagonistic effect (may reduce efficacy) Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Anorexia
  • CNS signs (depression, tremors, seizures)
  • Arthropathy in young animals
  • Acute renal failure (rare)

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce vomiting if recent ingestion and no contraindications. Administer activated charcoal to reduce absorption. Provide fluid therapy to maintain hydration and promote excretion. Control seizures with diazepam or barbiturates if necessary. Monitor renal and hepatic function. There is no specific antidote.

Food Animal Withdrawal Times

🥩 Meat: 5 days🥛 Milk: 3 days

Withdrawal times vary by country and formulation. For cattle, the meat withdrawal is typically 5 days (for injectable) and milk withdrawal is 3 days. For poultry, enrofloxacin is not approved in many countries; if used extra-label, withdrawal times may be longer. Always consult local regulations.

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).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep container tightly closed. Do not freeze injectable solutions.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and cats (oral and injectable). Not approved for food animals in the US, but extra-label use is allowed under AMDUCA.

Extra-Label (Off-Label) Use: In the US, enrofloxacin is approved for use in dogs and cats. Extra-label use in food animals is permitted under AMDUCA with a valid veterinary-client-patient relationship, but must follow withdrawal times and residue avoidance. Use in poultry is prohibited in the US due to concerns about fluoroquinolone resistance.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Enrofloxacin is a broad-spectrum bactericidal antibiotic commonly used in veterinary practice for a variety of infections. It is particularly valuable for treating infections caused by Gram-negative bacteria, including Pseudomonas, and Mycoplasma. Due to its excellent tissue penetration, it is effective for deep-seated infections such as prostatitis, pyoderma, and pneumonia. However, its use in young animals is limited due to the risk of cartilage damage, and in cats, high doses can cause retinal toxicity. In food animals, extra-label use is regulated, and withdrawal times must be strictly observed. Resistance to fluoroquinolones is a growing concern, so enrofloxacin should be reserved for cases where other antibiotics are ineffective or inappropriate. Always perform culture and sensitivity testing when possible, and use the lowest effective dose for the shortest duration to minimize resistance development.

References & Literature

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