替硝唑
**替硝唑 (Tinidazole)** 是一種第二代 **5-硝基咪唑類 (5-nitroimidazole)** 抗菌與抗原蟲藥物，其結構與藥理作用與甲硝唑 (metronidazole) 相似。 主要臨床重點包括： * **半衰期較長**：與甲硝唑相比，替硝唑的作用時間更長，因此給藥頻率較低（例如貓可每日一次，而甲硝唑需每日兩次）。 * **抗厭氧菌效力**：對絕對厭氧菌具有極佳的抗菌活性，特別是犬牙齦中常見的*Porphyromonas* spp.，使其在嚴重的牙科與口腔感染中非常有用。 * **抗原蟲活性**：可作為治療梨形鞭毛蟲 (Giardia)、溶組織內阿米巴 (Entamoeba histolytica)、滴蟲 (Trichomonas) 及小袋纖毛蟲 (Balantidium) 感染的替代療法。 * **胎兒三毛滴蟲 (Tritrichomonas foetus)**：雖然羅硝唑 (ronidazole) 通常是治療貓 T. foetus 的首選藥物，但替硝唑也曾被研究作為替代方案，儘管在某些情況下它可能僅能抑制排蟲而無法完全根除。 > **臨床提示**：由於該藥物具有極度苦味，強烈建議將其配製成膠囊或添加重口味調味劑的懸浮液，特別是對於容易因苦味而過度流涎或拒藥的貓咪患者。
作用機制: Tinidazole is a prodrug that requires activation within susceptible organisms. * **Uptake**: The drug diffuses into the target anaerobic bacteria or protozoa. * **Reduction**: Inside the cell, the nitro group of tinidazole is reduced by electron-transport proteins (such as **ferredoxin** or **nitroreductase** enzymes) specific to anaerobic metabolism. * **DNA Disruption**: This reduction → generates highly reactive, unidentified polar nitro radical anions → these radicals bind to and disrupt **DNA and nucleic acid synthesis** → leading to strand breakage and rapid cell death. This mechanism makes it rapidly **bactericidal**, **trichomonacidal**, and **amebicidal**.
各物種劑量
- Stomatitis, anaerobic infections · 15 mg/kg PO q24h · PO · q24h · 7 days
- Tritrichomonas foetus (experimental) · 30 mg/kg PO once daily · PO · q24h · 14 days · Decreased fecal shedding but failed to eradicate infection in 2 of 4 cats.
- Susceptible anaerobic infections · 10-15 mg/kg PO q12h · PO · q12h
- Stomatitis, anaerobic infections · 15-25 mg/kg PO q12h · PO · q12h · 7 days
- Giardiasis · 44 mg/kg PO q24h · PO · q24h · 6 days · Potentially useful for trichomoniasis, amebiasis, and balantidiasis.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to tinidazole or other 5-nitroimidazoles (e.g., metronidazole, ronidazole)
- Food-producing animals (prohibited use)
不良反應
- Vomiting
- Inappetence
- Diarrhea
- Neurotoxicity (ataxia, nystagmus, seizures)
- Hypersalivation (due to bitter taste)
藥物相互作用
- Alcohol · May induce a disulfiram-like reaction (nausea, vomiting, cramps).
- Cimetidine · May decrease the metabolism of tinidazole and increase the likelihood of dose-related side effects.
- Ketoconazole · May decrease the metabolism of tinidazole and increase the likelihood of dose-related side effects.
- Cyclosporine · Tinidazole may increase the serum levels of cyclosporine.
- Tacrolimus (systemic) · Tinidazole may increase the serum levels of tacrolimus.
- Fluorouracil (systemic) · Tinidazole may increase the serum levels of fluorouracil and increase the risk of toxicity.
- Lithium · Tinidazole may increase lithium serum levels and increase the risk for lithium toxicity.
- Oxytetracycline · May antagonize the therapeutic effects of metronidazole (and presumably tinidazole).
- Phenobarbital · May increase the metabolism of tinidazole thereby decreasing blood levels.
- Rifampin · May increase the metabolism of tinidazole thereby decreasing blood levels.
- Phenytoin · May increase the metabolism of tinidazole thereby decreasing blood levels.
- Warfarin · May prolong the prothrombin time (PT). Avoid concurrent use if possible; otherwise, intensify monitoring.
監測
- Clinical efficacy in treating the infection
- Gastrointestinal tolerance
- Neurological signs (ataxia, nystagmus, seizures)
過量
Very limited information is available. In rodent studies, the oral LD50 was >3.6 g/kg (mice) and >2 g/kg (rats). Treatment of acute overdoses is **symptomatic and supportive**. * **Decontamination**: Gastric lavage or induction of emesis may be helpful if performed shortly after ingestion and the patient is neurologically appropriate. * **Clearance**: Hemodialysis can remove approximately 43% of the drug in the body (based on human data) in a 6-hour session.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。