Orbifloxacin
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.
กลไกการออกฤทธิ์: 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.
ขนาดยาตามชนิดสัตว์
- Susceptible infections · 2.5 mg/kg-7.5 mg/kg · PO · once daily · Tablets. Higher end of the dosing range may be necessary for complicated infections.
- Skin infections (wounds and abscesses) · 7.5 mg/kg · PO · once daily · Suspension. For susceptible strains of S. aureus, E. coli, and P. multocida.
- Skin and other soft tissue infections · 7.5 mg/kg · PO · q24h · Caution with higher doses due to risk of retinal blindness.
- Susceptible infections · 5 mg/kg · PO · once daily
- Susceptible infections · 7.5 mg/kg · PO · once daily
- Susceptible infections · 2.5 mg/kg-7.5 mg/kg · PO · once daily · 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) · 2.5-7.5 mg/kg · PO · once daily · Suspension.
- Bacterial cystitis · 2.5 mg/kg · PO · q24h
- Skin and other soft tissue infections · 7.5 mg/kg · PO · q24h
วิธีการให้ยา
ข้อห้ามใช้
- 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)
อาการไม่พึงประสงค์
- 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)
อันตรกิริยาระหว่างยา
- Antacids / Dairy Products · Cations (Mg++, Al+++, Ca++) bind to orbifloxacin and prevent its absorption; separate doses by at least 2 hours.
- Other Antibiotics (Aminoglycosides, 3rd-gen cephalosporins, extended-spectrum penicillins) · Unpredictable synergism may occur against some bacteria (particularly Pseudomonas aeruginosa).
- Cyclosporine · May exacerbate nephrotoxicity and reduce the metabolism of systemic cyclosporine.
- Flunixin · May increase the AUC and elimination half-life of fluoroquinolones.
- Glyburide · Severe hypoglycemia is possible.
- Iron, Zinc (oral) · Decreased orbifloxacin absorption; separate doses by at least 2 hours.
- Methotrexate · Increased methotrexate levels possible, resulting in toxicity.
- Nitrofurantoin · May antagonize the antimicrobial activity of fluoroquinolones; concomitant use is not recommended.
- Phenytoin · May alter phenytoin levels.
- Probenecid · Blocks tubular secretion, potentially increasing blood levels and half-life of orbifloxacin.
- Sucralfate · May inhibit absorption of orbifloxacin; separate doses by at least 2 hours. · major
- Theophylline · May increase theophylline blood levels. · major
การติดตาม
- Clinical efficacy (resolution of infection)
- Gastrointestinal signs (appetite, vomiting, diarrhea)
- Vision changes or pupillary dilation in cats
- Neurological signs (seizures) in predisposed patients
การได้รับยาเกินขนาด
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.
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