Difloxacin Hydrochloride

Fluoroquinolone antibiotic Fluoroquinolones

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 5-10 mg/kg q24h Duration: 5-14 days depending on infection
Notes: For urinary tract infections, 5 mg/kg q24h for 10 days is common. For skin infections, 10 mg/kg q24h for 14 days.
Cat PO 5-10 mg/kg q24h Duration: 5-14 days
Notes: Use lower end for urinary tract infections, higher for skin infections.
Horse PO 5-7.5 mg/kg q24h Duration: 5-10 days
Notes: Oral administration may be associated with GI upset; monitor for diarrhea.
Cattle SC 10 mg/kg q24h Duration: 3-5 days
Notes: Extra-label; not approved for food animals in many countries. Withdrawal times must be observed.
Chicken PO (drinking water) 10 mg/kg body weight per day q24h Duration: 3-5 days
Notes: Administer in drinking water; ensure adequate water intake.
Rabbit PO 10-15 mg/kg q24h Duration: 7-14 days
Notes: Extra-label; monitor for GI disturbances.

Clinical Indications & Species Uses

General Indications
  • Treatment of infections caused by susceptible Gram-negative and Gram-positive bacteria, including Mycoplasma spp.
Dog (Canine)
  • Treatment of urinary tract infections caused by susceptible strains of E. coli, Proteus mirabilis, and Staphylococcus spp.
  • Treatment of skin and soft tissue infections (pyoderma, wounds) caused by susceptible staphylococci and Gram-negative bacteria.
Cat (Feline)
  • Treatment of urinary tract infections caused by susceptible bacteria.
  • Treatment of skin and soft tissue infections.
Horse (Equine)
  • Treatment of respiratory tract infections caused by susceptible bacteria (e.g., Rhodococcus equi, Streptococcus zooepidemicus).
  • Treatment of susceptible bacterial infections of the skin and urinary tract.
Cattle (Bovine)
  • Treatment of bovine respiratory disease (BRD) associated with Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni.
  • Treatment of acute E. coli mastitis (extra-label).
Small Ruminants (Sheep / Goat)
  • Treatment of respiratory infections (e.g., pasteurellosis) in sheep and goats (extra-label).
  • Treatment of enteric infections caused by susceptible E. coli.
Rabbit & Small Mammals
  • Treatment of respiratory infections (e.g., Pasteurella multocida) (extra-label).
  • Treatment of urinary tract infections.
Avian & Poultry
  • Treatment of colibacillosis in chickens and turkeys.
  • Treatment of mycoplasmosis in chickens and turkeys.
  • Treatment of fowl cholera (Pasteurella multocida) in chickens.
Exotic & Other Species
  • Treatment of susceptible bacterial infections in reptiles (e.g., shell rot, respiratory infections) (extra-label).
  • Treatment of bacterial infections in small mammals (e.g., guinea pigs, rats) (extra-label).

Pharmacology & Mechanism of Action

Drug Class: Fluoroquinolone antibiotic | Pharmacological Group: Fluoroquinolones

Mechanism of Action: Difloxacin is a fluoroquinolone antibacterial 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. Difloxacin is bactericidal and exhibits concentration-dependent killing.

Pharmacodynamics: Difloxacin has a broad spectrum of activity against Gram-positive and Gram-negative bacteria, including many pathogens of veterinary importance such as Escherichia coli, Pasteurella multocida, Mannheimia haemolytica, Staphylococcus spp., and Mycoplasma spp. It is particularly effective against Enterobacteriaceae and some Pseudomonas aeruginosa strains. The post-antibiotic effect is prolonged, allowing for once-daily dosing in some species. Difloxacin is more active against Gram-negative bacteria than some older fluoroquinolones but has variable activity against anaerobes and Streptococcus spp.

⚡ Pharmacokinetics Summary

Absorption: Difloxacin is well absorbed after oral administration in most species. In dogs, oral bioavailability is approximately 100%. In chickens, oral bioavailability is also high. Absorption is slightly delayed by food but not significantly reduced.
Distribution: Difloxacin is widely distributed throughout the body, achieving high concentrations in tissues and body fluids. It penetrates well into the prostate, lung, kidney, skin, and bone. It crosses the blood-brain barrier to a limited extent. Volume of distribution is large, indicating extensive tissue penetration.
Metabolism: Difloxacin undergoes minimal hepatic metabolism. The primary metabolite is the N-demethylated derivative, which retains some antibacterial activity. In some species, glucuronide conjugates are formed.
Excretion: Difloxacin is eliminated primarily by renal excretion (glomerular filtration and tubular secretion) and also via biliary excretion. In dogs, approximately 40-50% of the dose is excreted unchanged in urine, with the remainder as metabolites. In chickens, both renal and biliary routes contribute to elimination.
Half-Life: Dogs: 8-10 hours; Cats: 6-8 hours; Horses: 4-6 hours; Cattle: 6-8 hours; Chickens: 4-6 hours.
Bioavailability: Oral bioavailability is high: dogs ~100%, chickens ~80-90%, cattle ~70-80%.
Protein Binding: Difloxacin is moderately protein-bound, approximately 30-50% in most species.

Available Formulations & Strengths

Oral Tablet 50 mg, 100 mg, 200 mg (PO)
Oral Solution 10% solution (100 mg/mL) (PO)
Injectable Solution 5% solution (50 mg/mL) (SC, IM)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to difloxacin or other fluoroquinolones.
  • Use in growing animals (except where specifically indicated) due to potential cartilage damage.
  • Use in animals with known central nervous system disorders (e.g., epilepsy) as fluoroquinolones may lower seizure threshold.
  • Concurrent use with theophylline, warfarin, or antiarrhythmic agents (e.g., procainamide) without careful monitoring.
  • Use in pregnant or lactating animals unless benefits outweigh risks (safety not established).
Warnings & Clinical Precautions:
  • Use with caution in young animals (less than 8 months in dogs, less than 12 months in large breeds) due to potential arthropathy.
  • Use with caution in animals with renal or hepatic impairment; dose adjustment may be necessary.
  • In horses, oral administration may cause diarrhea; monitor hydration status.
  • In food animals, extra-label use is prohibited in some countries; observe withdrawal times.
  • Fluoroquinolones may cause photosensitivity; avoid excessive sunlight exposure during treatment.
  • Use in cats may cause ocular toxicity at high doses; avoid overdose.
  • Do not use in animals with a history of tendonitis or tendon rupture.

Adverse Effects & Reactions

Common:

  • Gastrointestinal disturbances (vomiting, diarrhea, anorexia)
  • Injection site reactions (pain, swelling) after SC/IM administration

Serious / Severe:

  • Cartilage erosion in young animals
  • Central nervous system stimulation (seizures, ataxia)
  • Acute renal failure (rare)
  • Hepatotoxicity (rare)

Rare:

  • Ocular toxicity in cats (retinal degeneration)
  • Blood dyscrasias (leukopenia, thrombocytopenia)
  • Allergic reactions (anaphylaxis)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Antacids containing aluminum, magnesium, or calcium Reduced absorption of difloxacin due to chelation; administer at least 2 hours apart. Moderate
Sucralfate Reduced absorption of difloxacin; separate administration by at least 2 hours. Moderate
Theophylline Increased plasma theophylline levels, risk of toxicity; monitor levels and adjust dose. High
Warfarin Increased anticoagulant effect; monitor coagulation parameters. Moderate
Nonsteroidal anti-inflammatory drugs (NSAIDs) Increased risk of CNS stimulation and seizures; avoid concurrent use. High
Corticosteroids Increased risk of tendon rupture; avoid concurrent use. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Ataxia
  • Seizures
  • Depression
  • Arthrotoxicity in young animals

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce emesis if recent oral ingestion. 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.

Food Animal Withdrawal Times

🥩 Meat: 5 days🥛 Milk: 3 days🥚 Eggs: 5 days

Withdrawal times are based on extra-label use in cattle and poultry; actual times may vary by country and formulation. 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).

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

Handling & Special Conditions: Protect from light and moisture. Keep container tightly closed.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Difloxacin is not FDA-approved for veterinary use in the US. It is approved in some other countries for use in poultry and swine. In the US, it may be used extra-label in companion animals.

Extra-Label (Off-Label) Use: In the US, extra-label use of fluoroquinolones in food-producing animals is prohibited by the FDA (since 1997). In other countries, use may be permitted under veterinary supervision with appropriate withdrawal times. For companion animals, extra-label use is allowed under AMDUCA.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Difloxacin is a broad-spectrum fluoroquinolone with excellent activity against many veterinary pathogens. It is particularly useful for respiratory and urinary tract infections. Its long half-life allows once-daily dosing, improving compliance. However, its use in food animals is restricted in many regions due to concerns about antimicrobial resistance. In companion animals, it is a valuable option for infections caused by multidrug-resistant bacteria. Always culture and sensitivity testing before use. Monitor for adverse effects, especially in young animals and those with renal impairment. Avoid concurrent use with NSAIDs and theophylline. Provide adequate hydration during therapy.

References & Literature

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