オルビフロキサシン
Orbifloxacin
4-fluoroquinolone
別名: Orbax · Posatex · Marufloxacin · Orbifloxacino · Orbifloxacinum
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| 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.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| 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.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections | 5 mg/kg | PO | once daily | — | 🌎 NA |
| Susceptible infections | 7.5 mg/kg | PO | once daily | — | 🌎 NA |
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
オルビフロキサシンは、主に獣医学で使用される合成広域フルオロキノロン系抗生物質です。濃度依存性の殺菌作用を示し、有意なポストアンチバイオティックエフェクト（PAE）を持ちます。これは、薬物濃度が最小発育阻止濃度（MIC）を下回った後でも細菌の増殖が抑制され続けることを意味します。
好気性グラム陰性桿菌（大腸菌、クレブシエラ、プロテウス、エンテロバクター、パスツレラなど）および一部のグラム陽性球菌（スタフィロコッカス・インターメディウス、黄色ブドウ球菌など）に対して高い有効性を示します。
臨床のポイント： 他のフルオロキノロン系と同様に、オルビフロキサシンは偏性嫌気性菌およびほとんどの腸球菌に対する有効性が低いです。抗菌薬の適正使用を促進するため、培養および感受性試験で必要性が示された感染症に限定して使用すべきです。
作用機序
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.
安全性・警告
禁忌
- 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)
有害事象
- 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)
注意事項
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.
医薬品相互作用
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)
監視
- Clinical efficacy (resolution of infection)
- Gastrointestinal signs (appetite, vomiting, diarrhea)
- Vision changes or pupillary dilation in cats
- Neurological signs (seizures) in predisposed patients
薬物動態
半減期
吸収
Nearly completely absorbed after oral administration in dogs and cats. In horses, oral bioavailability is approximately 70%.
分布
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).
代謝
Approximately 50% of the drug is excreted unchanged.
消失
Eliminated primarily via the kidneys. Urine levels remain well above MICs for susceptible organisms for at least 24 hours after dosing.
過剰投与
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.
製品
製剤
- Oral tablets
- 30 mg/ml oral suspension
- 8.5 mg/ml otic drops (combined with mometasone and posaconazole)
動物用医薬品
- 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
規制ステータス
POM-V
POM-V
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
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.
飼主向け情報
- 投与方法： 獣医師の指示通りに正確に投薬してください。ペットの具合が良くなったように見えても、抗生物質耐性菌の発生を防ぐため、自己判断で投薬を中止しないでください。
- 食事との相互作用： この薬を乳製品（チーズや牛乳など）、制酸剤、またはカルシウム、鉄、亜鉛を含むサプリメントと同時に与えないでください。これらは薬の吸収を妨げる可能性があります。少なくとも2時間の間隔を空けてください。
- 副作用： 最も一般的な副作用は、嘔吐、下痢、または食欲不振です。これらの症状がひどい場合は獣医師に連絡してください。
猫の飼い主様への重要な注意： まれに、このクラスの薬は猫に視力障害を引き起こす可能性があります。猫の瞳孔が異常に開いている、または目が見えにくそうにしていることに気づいた場合は、直ちに投薬を中止し、獣医師に連絡してください。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。