Orbifloxacin
4-fluoroquinolone
Also known as: Orbax · Posatex · Marufloxacin · Orbifloxacino · Orbifloxacinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 2.5 mg/kg-7.5 mg/kg | PO | once daily | — | 🌎 NA |
| Urinary tract infections (cystitis) and skin/soft tissue infections (wounds and abscesses) | 2.5-7.5 mg/kg | PO | once daily | — | 🌎 NA |
| Bacterial cystitis | 2.5 mg/kg | PO | q24h | — | 🌍 EU |
| Skin and other soft tissue infections | 7.5 mg/kg | PO | q24h | — | 🌍 EU |
| Otitis | 2-8 drops per ear | topical | q24h | — | 🌍 EU |
- Susceptible infections: Tablets. Higher end of the dosing range may be necessary in hospitalized patients, those with underlying disease, structural alterations, or infections caused by 'problem' pathogens.
- Urinary tract infections (cystitis) and skin/soft tissue infections (wounds and abscesses): Suspension.
- Otitis: Number of drops is determined by the weight of the dog.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 2.5 mg/kg-7.5 mg/kg | PO | once daily | — | 🌎 NA |
| Skin infections (wounds and abscesses) | 7.5 mg/kg | PO | once daily | — | 🌎 NA |
| Skin and other soft tissue infections | 7.5 mg/kg | PO | q24h | — | 🌍 EU |
- Susceptible infections: Tablets. Higher end of the dosing range may be necessary for complicated infections.
- Skin infections (wounds and abscesses): Suspension. For susceptible strains of S. aureus, E. coli, and P. multocida.
- Skin and other soft tissue infections: Caution with higher doses due to risk of retinal blindness.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 5 mg/kg | PO | once daily | — | 🌎 NA |
| Susceptible infections | 7.5 mg/kg | PO | once daily | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Orbifloxacin is a synthetic, broad-spectrum fluoroquinolone antibiotic used primarily in veterinary medicine. It exhibits concentration-dependent bactericidal activity and possesses a significant post-antibiotic effect (PAE), meaning bacterial growth continues to be suppressed even after drug concentrations fall below the minimum inhibitory concentration (MIC).
It is highly effective against aerobic gram-negative bacilli (e.g., E. coli, Klebsiella, Proteus, Enterobacter, Pasteurella) and some gram-positive cocci (e.g., Staphylococcus intermedius, S. aureus).
Clinical Pearl: Like other fluoroquinolones, orbifloxacin has poor efficacy against obligate anaerobes and most Enterococcus species. It should be reserved for infections where culture and susceptibility testing indicate its necessity, promoting responsible antimicrobial stewardship.
Mechanism of action
Fluoroquinolones exert their bactericidal effect by targeting two essential bacterial enzymes:
- DNA Gyrase (Topoisomerase II): The primary target in gram-negative bacteria. It prevents the relaxation of positively supercoiled DNA, which is required for normal transcription and replication.
- Topoisomerase IV: The primary target in gram-positive bacteria. It interferes with the separation of interlinked replicated DNA molecules.
Mechanism Pathway: Orbifloxacin binds to the enzyme-DNA complex → inhibits DNA replication and transcription → induces double-stranded DNA breaks → rapid bacterial cell death.
Safety & warnings
Contraindications
- Immature dogs during the rapid growth phase (2-8 months in small/medium breeds; up to 18 months in large/giant breeds)
- Known hypersensitivity to orbifloxacin or other quinolones
- Giant-breed dogs <18 months old
- Large breeds <12 months old
- Small and medium-sized breeds <8 months old
- Pregnant or lactating bitches
- Animals intended for breeding
- Animals <4 months of age (otic preparation)
- Animals with a ruptured tympanum (otic preparation)
Adverse effects
- Anorexia
- Vomiting
- Diarrhea
- Arthropathies (cartilage damage) in immature, growing animals
- Potential retinal toxicity/blindness in cats (rare, but reported with higher doses of fluoroquinolones)
- CNS stimulation (rare)
- Cartilage abnormalities in growing animals
- CNS adverse effects (potentiated by NSAIDs)
- Retinal blindness in cats (dose-dependent)
Precautions
Use with caution in animals with known or suspected CNS disorders (e.g., seizure disorders) as fluoroquinolones have rarely been associated with CNS stimulation. Safety in breeding or pregnant dogs and cats has not been established. Use higher dosages carefully in cats due to the potential risk of retinal toxicity.
Drug interactions
Cations (Mg++, Al+++, Ca++) bind to orbifloxacin and prevent its absorption; separate doses by at least 2 hours.
Unpredictable synergism may occur against some bacteria (particularly Pseudomonas aeruginosa).
May exacerbate nephrotoxicity and reduce the metabolism of systemic cyclosporine.
May increase the AUC and elimination half-life of fluoroquinolones.
Severe hypoglycemia is possible.
Decreased orbifloxacin absorption; separate doses by at least 2 hours.
Increased methotrexate levels possible, resulting in toxicity.
May antagonize the antimicrobial activity of fluoroquinolones; concomitant use is not recommended.
May alter phenytoin levels.
Blocks tubular secretion, potentially increasing blood levels and half-life of orbifloxacin.
May inhibit absorption of orbifloxacin; separate doses by at least 2 hours.
May increase theophylline blood levels.
Potential for increased warfarin effects.
Binds fluoroquinolones, preventing GI absorption
Inhibits absorption; separate dosing by at least 2 hours
May reduce the clearance of fluoroquinolones
Decreased metabolism and increased nephrotoxicity
Decreased metabolism and increased nephrotoxicity
May increase anticoagulant action
Potentiates CNS adverse effects (seizures)
Monitoring
- Clinical efficacy (resolution of infection)
- Gastrointestinal signs (appetite, vomiting, diarrhea)
- Vision changes or pupillary dilation in cats
- Neurological signs (seizures) in predisposed patients
Pharmacokinetics
Half-life
Absorption
Nearly completely absorbed after oral administration in dogs and cats. In horses, oral bioavailability is approximately 70%.
Distribution
Distributes well into tissues. Volume of distribution (Vd) is 1.5 L/kg in dogs and 1.4 L/kg in cats. Protein binding is low (8% in dogs, 15% in cats, approx. 20% in horses).
Metabolism
Approximately 50% of the drug is excreted unchanged.
Elimination
Eliminated primarily via the kidneys. Urine levels remain well above MICs for susceptible organisms for at least 24 hours after dosing.
Overdose
In dogs, receiving up to 5X the maximum dose (37.5 mg/kg) for 30 days did not result in any significant adverse effects. In cats, receiving higher dosages exhibited soft feces and decreased body weight gains.
Available products
Formulations
- Oral tablets
- 30 mg/ml oral suspension
- 8.5 mg/ml otic drops (combined with mometasone and posaconazole)
Veterinary
- Orbifloxacin Oral Tablets: 5.7 mg, 22.7 mg, 68 mg (Orbax)
- Orbifloxacin Oral Suspension: 30 mg/mL (Orbax Suspension)
- Orbax 30 mg/ml oral suspension
- Posatex otic drops
Regulatory status
POM-V
POM-V
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets should be stored between 2-30°C (36-86°F) and protected from excessive moisture. Oral suspension should be stored between 2-25°C (36-77°F); it does not require refrigeration. Store upright and shake well before use. Compounded mixtures with calcium or magnesium (e.g., Lixotinic) show significant inactivation within 4 days.
Client information
- Administration: Give this medication exactly as prescribed by your veterinarian. Do not stop giving it early, even if your pet seems to feel better, to prevent antibiotic-resistant infections.
- Food Interactions: Do not give this medication at the same time as dairy products (like cheese or milk), antacids, or supplements containing calcium, iron, or zinc. These can block the drug from being absorbed. Separate these by at least 2 hours.
- Side Effects: The most common side effects are vomiting, diarrhea, or loss of appetite. Contact your vet if these become severe.
Important Note for Cat Owners: Rarely, this class of drugs can cause vision problems in cats. If you notice your cat's pupils are unusually large or they seem to have trouble seeing, stop the medication and contact your veterinarian immediately.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.