ジフロキサシン
ジフロキサシンは、主に犬の感受性細菌感染症の治療に適応される動物専用の**フルオロキノロン系抗菌薬**です。 **主な臨床的特徴:** * **腎臓への負担軽減:** 腎排泄に大きく依存する他の多くのフルオロキノロン系とは異なり、ジフロキサシンは広範な肝胆道排泄を受けます（80%以上が糞便中に排泄）。そのため、中等度から重度の腎不全の犬において、毒性レベルまで蓄積しにくく、独自の利点があります。 * **抗菌スペクトル:** 多くのグラム陰性および陽性桿菌・球菌（クレブシエラ、ブドウ球菌、大腸菌、エンテロバクター、カンピロバクター、プロテウス、パスツレラなど）に対して良好な有効性を示します。 * **制限事項:** ほとんどの嫌気性菌に対する活性は弱く、腸球菌には通常無効です。一部の緑膿菌株も耐性を示す場合があります。 > **臨床のポイント:** フルオロキノロン系は濃度依存性の殺菌薬です。最小発育阻止濃度（MIC）に対する最高血中濃度（Cmax）を最大化することが、臨床的有効性と耐性菌の予防において重要です。
作用機序: Difloxacin is a concentration-dependent bactericidal agent. * It actively enters the bacterial cell and targets **DNA-gyrase** (a type-II topoisomerase) and topoisomerase IV. * Inhibition of these enzymes → prevents DNA supercoiling and uncoiling → halts DNA synthesis and transcription. * The net result is rapid disruption of bacterial cell replication and subsequent cell death.
動物種別の用量
- Susceptible infections (MIC ≤ 0.25 micrograms/mL) · 7.5 mg/kg · PO · q24h · Administer non-fasted. Appears safe and adequately absorbed, but further investigation is warranted. Unknown if it should be avoided in young, growing horses.
- Susceptible infections · 5-10 mg/kg · PO · q24h · 2-3 days beyond the cessation of clinical signs (maximum 30 days) · Administer preferably on an empty stomach, unless GI upset occurs.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Hypersensitivity to difloxacin or other quinolones
- Immature dogs during the rapid growth phase (2-8 months in small/medium breeds; up to 18 months in large/giant breeds)
- Cats (relative contraindication due to nausea/vomiting and unknown ophthalmic/retinal safety)
- Food-producing animals (extra-label use prohibited by federal law)
有害事象
- Anorexia
- Vomiting
- Diarrhea
- Cartilage abnormalities (arthropathies) in growing animals
- CNS stimulation or seizures (rare)
- Facial erythema and edema (at high doses)
- Weight loss (at high doses)
薬物相互作用
- Antacids (Mg++, Al+++, Ca++) · May bind to difloxacin and prevent its absorption; separate doses by at least 2 hours.
- Dairy Products · Calcium content may decrease absorption; separate doses by at least 2 hours.
- 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.
- Glyburide · Severe hypoglycemia is possible.
- Iron and Zinc supplements · Decreased difloxacin 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 · Difloxacin may alter phenytoin blood levels.
- Probenecid · May block tubular secretion and increase the blood level and half-life of difloxacin.
- Sucralfate · May inhibit absorption of difloxacin; separate doses by at least 2 hours.
- Theophylline · Difloxacin may increase theophylline blood levels, potentially leading to toxicity.
モニタリング
- Clinical efficacy (resolution of infection)
- Gastrointestinal signs (appetite, vomiting, diarrhea)
- CNS signs (especially in patients with a history of seizures)
過量投与
In dogs, doses up to 2.5X the maximum recommended dose (25 mg/kg) for 30 days did not cause overly significant adverse effects. Observed signs included facial erythema/edema, diarrhea, decreased appetite, and weight loss. Treatment should be supportive and symptomatic.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。