Baytril (Enrofloxacin)

Fluoroquinolone antibiotic Antibacterial

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 5-20 mg/kg q24h Duration: 5-14 days (depending on infection)
Notes: Higher doses (20 mg/kg) may be used for severe infections. For pyoderma, treat for at least 2-3 weeks beyond clinical resolution.
Dog IV/IM 5-10 mg/kg q24h Duration: 5-7 days
Notes: IV administration should be slow (over 30 minutes) to avoid adverse effects. IM may cause pain at injection site.
Cat PO 5-10 mg/kg q24h Duration: 5-14 days
Notes: Cats may be more sensitive to ocular effects; use with caution in cats with renal disease.
Cat IV/IM 5 mg/kg q24h Duration: 5-7 days
Notes: IM injection may cause pain; IV should be slow.
Horse PO 5-7.5 mg/kg q24h Duration: 5-10 days
Notes: Oral absorption is variable; consider IV for severe infections. Not recommended in foals due to cartilage damage risk.
Horse IV 5-7.5 mg/kg q24h Duration: 5-10 days
Notes: Administer slowly over 30 minutes. Avoid in growing horses due to arthropathy risk.
Cattle SC 7.5-12.5 mg/kg q24h (single dose for BRD) Duration: 1-3 days
Notes: Subcutaneous injection in the neck. Withdrawal times must be observed.
Cattle IV 5-10 mg/kg q24h Duration: 3-5 days
Notes: For severe infections. Not for use in lactating dairy cattle in some countries.
Sheep/Goat PO 5-10 mg/kg q24h Duration: 3-5 days
Notes: Off-label use; withdrawal times may be extended.
Rabbit PO 5-15 mg/kg q24h Duration: 7-14 days
Notes: May be compounded into oral suspension. Monitor for GI upset.
Poultry PO (drinking water) 10-15 mg/kg q24h Duration: 3-5 days
Notes: Administer in drinking water; ensure adequate water intake. Withdrawal times apply.
Reptiles IM 5-10 mg/kg q24-48h Duration: 7-14 days
Notes: Dose may vary by species; consult a specialist.

Clinical Indications & Species Uses

General Indications
  • Treatment of bacterial infections caused by susceptible organisms in various species
Dog (Canine)
  • Treatment of bacterial infections of the skin, respiratory tract, urinary tract, gastrointestinal tract, and soft tissue infections
  • Prostatitis
  • Pyoderma
  • Otitis externa (when caused by susceptible bacteria)
  • Wound infections
Cat (Feline)
  • Treatment of bacterial infections of the skin, respiratory tract, urinary tract, and gastrointestinal tract
  • Abscesses
  • Wound infections
  • Chlamydophila felis infections
Horse (Equine)
  • Treatment of respiratory tract infections (e.g., pneumonia, pleuropneumonia) caused by susceptible bacteria
  • Soft tissue infections
  • Septicemia in foals (off-label use)
Cattle (Bovine)
  • Treatment of bovine respiratory disease (BRD) associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni
  • Treatment of acute E. coli mastitis (in some countries)
  • Metritis (off-label)
Small Ruminants (Sheep / Goat)
  • Treatment of respiratory infections (e.g., pneumonia) in sheep and goats
  • Enteric infections (off-label)
  • Mastitis (off-label)
Rabbit & Small Mammals
  • Treatment of respiratory infections (e.g., Pasteurella multocida)
  • Urinary tract infections
  • Abscesses (adjunct to surgical drainage)
Avian & Poultry
  • Treatment of colibacillosis (E. coli infections)
  • Mycoplasmosis
  • Salmonellosis
  • Pasteurellosis (fowl cholera)
  • Respiratory infections in poultry and companion birds
Exotic & Other Species
  • Reptiles: Treatment of bacterial infections (e.g., respiratory, skin, shell infections)
  • Small mammals (ferrets, guinea pigs): Respiratory and urinary infections
  • Amphibians: Bacterial infections

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 and uncoiling 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. It has a post-antibiotic effect (PAE) against susceptible organisms, meaning that bacterial growth is suppressed even after the drug concentration falls below the minimum inhibitory concentration (MIC). It is effective against a wide range of pathogens including E. coli, Salmonella, Pasteurella, Mycoplasma, and Pseudomonas. Resistance can develop via chromosomal mutations in the genes encoding DNA gyrase or topoisomerase IV, or via efflux pumps and plasmid-mediated resistance (qnr genes).

⚡ Pharmacokinetics Summary

Absorption: Enrofloxacin is well absorbed after oral administration in most species, with bioavailability ranging from 60-100% depending on species and formulation. In dogs and cats, oral bioavailability is approximately 80-100%. In horses, oral absorption is variable and may be lower. Food can delay absorption but does not significantly reduce the extent.
Distribution: Enrofloxacin is widely distributed throughout the body, achieving high concentrations in tissues, including the lungs, kidneys, liver, skin, bone, and prostate. It penetrates well into cells and body fluids, including cerebrospinal fluid (though lower than serum), synovial fluid, and milk. It crosses the placenta and is excreted in milk. Volume of distribution is large, typically 2-4 L/kg in dogs and cats.
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, approximately 10-20% is converted to ciprofloxacin, while in cats, the conversion is less. In some species, such as cattle and poultry, metabolism may be more extensive.
Excretion: Enrofloxacin and its metabolites are primarily excreted via the kidneys (glomerular filtration and tubular secretion) and also via the biliary route into feces. In dogs, about 30-50% is excreted unchanged in urine, with the remainder as metabolites. In cats, renal excretion is also significant. In ruminants, biliary excretion may be more important.
Half-Life: Dogs: 4-6 hours; Cats: 4-6 hours; Horses: 4-9 hours; Cattle: 2-4 hours; Pigs: 6-8 hours; Poultry: 7-11 hours.
Bioavailability: Oral bioavailability: Dogs ~80-100%, Cats ~100%, Horses ~50-60% (variable), Cattle ~80-100%, Poultry ~60-80%.
Protein Binding: Enrofloxacin is approximately 20-40% protein-bound in plasma, depending on species.

Available Formulations & Strengths

Oral Tablet 22.7 mg, 68 mg, 136 mg (PO)
Oral Solution (for drinking water) 10% solution (100 mg/mL) (PO)
Injectable Solution 50 mg/mL, 100 mg/mL (IV/IM/SC)
Oral Suspension (compounded) Various (e.g., 25 mg/mL) (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to enrofloxacin or other fluoroquinolones
  • Known or suspected allergy to the drug
  • Use in growing animals (especially dogs under 8 months of age, large breeds under 18 months, and horses under 2 years) due to risk of articular cartilage damage
  • Use in cats with known retinal degeneration or those with a history of retinal disease
  • Use in animals with known CNS disorders (e.g., epilepsy) as it may lower seizure threshold
  • Concurrent use with certain drugs that may increase risk of tendon damage (e.g., corticosteroids) - caution
Warnings & Clinical Precautions:
  • Use with caution in animals with renal or hepatic impairment; dose adjustment may be necessary.
  • In young animals, avoid use unless the benefits outweigh the risks due to potential cartilage damage.
  • In cats, high doses or prolonged use may cause retinal degeneration; monitor for visual changes.
  • May cause crystalluria in animals with alkaline urine; ensure adequate hydration.
  • Use with caution in animals with a history of seizures or epilepsy.
  • In horses, oral administration may cause diarrhea; monitor for GI disturbances.
  • For food animals, observe withdrawal times to avoid drug residues in meat and milk.
  • Avoid extra-label use in food animals unless permitted by veterinary oversight and appropriate withdrawal times are established.
  • Do not use in animals that are known to be carriers of resistant bacteria; culture and sensitivity testing is recommended before use.

Adverse Effects & Reactions

Common:

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

Serious / Severe:

  • Arthropathy (cartilage damage) in young animals
  • Retinal degeneration in cats (especially at high doses)
  • Seizures or CNS stimulation
  • Acute renal failure (rare)
  • Hepatotoxicity (rare)
  • Tendon rupture (rare)

Rare:

  • Allergic reactions (anaphylaxis)
  • Blood dyscrasias (leukopenia, thrombocytopenia)
  • Crystalluria
  • Photosensitivity
  • Cardiac arrhythmias (QT prolongation)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Antacids (aluminum, magnesium, calcium) Decreased absorption of enrofloxacin due to chelation; separate administration by 2-4 hours. Moderate
Sucralfate Reduced oral absorption of enrofloxacin; administer at least 2 hours apart. Moderate
Theophylline Enrofloxacin may increase theophylline levels, leading to toxicity; monitor levels and adjust dose. High
Warfarin Enrofloxacin may enhance anticoagulant effect; monitor coagulation parameters. Moderate
Corticosteroids Concurrent use may increase the risk of tendon rupture or cartilage damage. Moderate
Nitrofurantoin Antagonistic effect; avoid concurrent use. Moderate
Cyclosporine Enrofloxacin may increase cyclosporine levels; monitor for nephrotoxicity. Moderate
Nonsteroidal anti-inflammatory drugs (NSAIDs) Increased risk of CNS stimulation and seizures; use with caution. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Anorexia
  • Lethargy
  • CNS signs (tremors, seizures, ataxia)
  • Articular cartilage damage in young animals
  • Acute renal failure (with massive overdose)

Emergency Treatment Protocol: Treatment is primarily symptomatic and supportive. Induce vomiting if recent ingestion and the animal is conscious. Administer activated charcoal to reduce absorption. Provide intravenous fluids to maintain hydration and promote excretion. Control seizures with diazepam or barbiturates. Monitor renal and hepatic function. There is no specific antidote.

Food Animal Withdrawal Times

🥩 Meat: 7 days🥛 Milk: 3 days🥚 Eggs: 7 days

Withdrawal times vary by country and formulation. For cattle, the meat withdrawal is typically 7 days and milk 3 days (for injectable). For poultry, meat withdrawal is 7 days and eggs 7 days. Always follow local regulations and product label.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), with 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 in a tightly closed container. Do not freeze injectable solutions. Oral solutions should be used within the expiration date.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and cats (oral and injectable), and for cattle (injectable) for BRD. Not approved for horses, small ruminants, rabbits, or exotic animals; use in these species is extra-label.

Extra-Label (Off-Label) Use: Extra-label use in food animals is permitted under AMDUCA (Animal Medicinal Drug Use Clarification Act) only with a valid veterinary-client-patient relationship, and must follow established withdrawal times. Use in poultry is prohibited in some countries due to concerns about resistance. In the US, enrofloxacin is not approved for use in poultry (except for day-old chicks for certain infections) due to fluoroquinolone resistance concerns.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Enrofloxacin is a broad-spectrum fluoroquinolone commonly used in veterinary practice for a variety of bacterial infections. It is particularly effective against Gram-negative and some Gram-positive organisms, as well as Mycoplasma. Due to its excellent tissue penetration, it is useful for deep-seated infections such as pyoderma, prostatitis, and pneumonia. However, its use in young animals is limited due to the risk of cartilage damage. In cats, high doses can cause retinal degeneration, so doses should be kept at the lower end of the range and treatment duration should be minimized. For food animals, strict adherence to withdrawal times is essential to prevent drug residues. Culture and sensitivity testing is recommended before initiating therapy to reduce the development of resistance. Enrofloxacin should be used judiciously as a second-line antibiotic in many cases to preserve its efficacy.

References & Literature

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