Ronidazole
**Ronidazole** is a potent **5-nitroimidazole** antibiotic and antiprotozoal agent. While structurally related to metronidazole, it exhibits superior efficacy against certain resistant protozoa. * Primarily utilized off-label in veterinary medicine for the eradication of **_Tritrichomonas foetus_** infections in cats, a notorious cause of chronic large bowel diarrhea. * Also employed in avian medicine to treat trichomoniasis (canker) in non-food birds (e.g., pigeons, finches). **Clinical Pearl**: Due to its extremely bitter taste and potential human health risks (suspected carcinogen), it must be carefully compounded into intact gelatin capsules. It is strictly prohibited for use in food-producing animals.
Mecanismo: 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.
Dosificación por especie
- 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.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- 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)
Efectos adversos
- Neurotoxicity (lethargy, anorexia, ataxia, nystagmus, seizures, behavior changes)
- Gastrointestinal effects (anorexia, vomiting)
- Carcinogenic potential (tumors in mice and rats)
- Testicular toxicity (reported in dogs)
Interacciones farmacológicas
- 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
Monitorización
- 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)
Sobredosis
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.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.