ロニダゾール
**ロニダゾール (Ronidazole)** は、強力な**5-ニトロイミダゾール系**の抗生物質および抗原虫薬です。メトロニダゾールと構造的に類似していますが、特定の耐性原虫に対してより優れた効果を示します。 * 主に獣医療において、猫の慢性大腸性下痢の原因となる**トリコモナス（*Tritrichomonas foetus*）**感染症の治療に適用外使用（オフラベル）として用いられます。 * また、非食用鳥類（ハトやフィンチなど）のトリコモナス症の治療にも使用されます。 **臨床上のポイント**: 非常に苦味が強く、人体への健康リスク（発がん性の疑い）があるため、カプセル剤として慎重に調剤する必要があります。食用動物への使用は厳格に禁止されています。
作用機序: Ronidazole is a prodrug that requires activation by protozoal organelles called **hydrogenosomes**. * Inside the hydrogenosome, the drug is reduced → forms **polar autotoxic anion radicals**. * These highly reactive radicals bind to and disrupt protozoal DNA → inhibition of nucleic acid synthesis → **cell death**. *Note*: While it shares this mechanism with metronidazole, ronidazole often retains activity against metronidazole-resistant _T. foetus_ strains, though resistance to ronidazole has been documented.
動物種別の用量
- treatment of T. foetus infections · 30 mg/kg PO q24h · PO · q24h · 14 days · Likely to be most effective in resolving diarrhea and eradicating T. foetus infection. Must be given in capsule form due to bitter taste.
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 ronidazole or other 5-nitroimidazoles (e.g., metronidazole)
- Food-producing animals (FDA prohibited)
- Pregnant or nursing cats (safety not established; use with extreme caution)
有害事象
- Neurotoxicity (lethargy, anorexia, ataxia, nystagmus, seizures, behavior changes)
- Gastrointestinal effects (anorexia, vomiting)
- Carcinogenic potential (tumors in mice and rats)
- Testicular toxicity (reported in dogs)
薬物相互作用
- Alcohol · May induce a disulfiram-like reaction (nausea, vomiting, cramps)
- Cimetidine · May decrease the metabolism of ronidazole and increase the likelihood of dose-related side effects
- Ketoconazole · May decrease the metabolism of ronidazole and increase the likelihood of dose-related side effects
- Cyclosporine · Ronidazole may increase the serum levels of cyclosporine
- Tacrolimus · Ronidazole may increase the serum levels of tacrolimus
- Fluorouracil · Ronidazole may increase the serum levels of fluorouracil and increase risk for toxicity
- Lithium · Ronidazole may increase lithium serum levels and increase risk for lithium toxicity
- Oxytetracycline · Reportedly may antagonize the therapeutic effects of metronidazole (and presumably ronidazole)
- Phenobarbital · May increase the metabolism of ronidazole thereby decreasing blood levels
- Rifampin · May increase the metabolism of ronidazole thereby decreasing blood levels
- Phenytoin · May increase the metabolism of ronidazole thereby decreasing blood levels
- Warfarin · May prolong INR/PT; avoid concurrent use if possible or intensify monitoring
モニタリング
- Clinical efficacy (diarrhea improvement)
- Adverse effects (neurotoxicity, vomiting, anorexia)
- PCR testing (to confirm infection; note that negative results after treatment do not conclusively prove eradication)
過量投与
Overdoses can cause severe **neurotoxicity**, hemorrhage, and death (as reported in society finches consuming ronidazole in drinking water). Cats receiving 50 mg/kg twice daily have a greater incidence of neurotoxicity. **Treatment**: * Discontinue further therapy immediately. * Treat supportively. * Consider administering a GABA inhibitor, such as **diazepam**, to competitively inhibit GABA receptors in the CNS and control neurological signs.
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。