Furazolidone
Furazolidone is a synthetic **nitrofuran-derivative** antibacterial and antiprotozoal agent. Historically, it was utilized in small animal medicine as a second-line treatment for enteric infections, particularly those caused by *Giardia*, *Coccidia*, and various bacterial enteropathogens (e.g., *Campylobacter*, *Salmonella*, *E. coli*). > **Clinical Pearl:** Due to the withdrawal of human commercial products in many countries and the strict FDA prohibition of its extralabel use in food-producing animals (due to carcinogenic concerns associated with nitrofurans), its use in modern veterinary practice is exceedingly rare. Safer and more readily available alternatives like fenbendazole and metronidazole are now the standard of care for giardiasis and similar enteric infections.
Mecanismo: Furazolidone acts as a prodrug. Inside susceptible organisms, it is reduced by **bacterial flavoproteins** (nitroreductases) → highly reactive intermediate compounds are formed → these intermediates cause severe oxidative damage to **ribosomal proteins, DNA, and RNA**, disrupting cellular metabolism and inhibiting protein synthesis. * **Antiprotozoal mechanism:** While not fully elucidated, it likely involves similar oxidative damage to essential protozoal enzymes. * **MAO Inhibition:** Furazolidone also acts as a **monoamine oxidase inhibitor (MAOI)** in the mammalian host, which can lead to significant drug and dietary interactions (e.g., with tyramine-rich foods or sympathomimetic drugs).
Dosificación por especie
- Giardia · 4 mg/kg PO twice daily (q12h) · PO · q12h · 7-10 days · If re-treatment is required, elevated dosages or lengthened treatment regimens may provide better results.
- Giardia · 4 mg/kg, PO twice daily (q12h) · PO · q12h · 7 days
- Cystoisospora spp. · 8-20 mg/kg PO q12-24h · PO · q12-24h · 5 days
- Coccidiosis · 8-20 mg/kg PO once daily · PO · q24h · 7 days
- Giardiasis · 4 mg/kg PO q12h · PO · q12h · 5-10 days
- Amebiasis · 2.2 mg/kg PO q8h · PO · q8h · 7 days
- Amebic colitis · 2.2 mg/kg PO q8h · PO · q8h · 7 days
- Coccidiosis · 8-20 mg/kg PO for one week · PO · Unknown · 1 week
- Giardia · 4 mg/kg PO q12h · PO · q12h · 5 days
- Susceptible infections · 4 mg/kg PO three times daily · PO · q8h
- Amebic colitis · 2.2 mg/kg PO q8h · PO · q8h · 7 days
Vías de administración
Contraindicaciones
- Known hypersensitivity to furazolidone or other nitrofurans
- Food-producing animals (FDA strictly prohibits extralabel use)
- Pregnant queens (per some references)
Efectos adversos
- Anorexia
- Vomiting
- Abdominal cramping
- Diarrhea
- Urine discoloration (dark yellow to brown)
Interacciones farmacológicas
- Alcohol · May cause a disulfiram-like reaction.
- Amitraz · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
- Buspirone · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
- Selegiline · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
- Sympathomimetic amines (phenylpropanolamine, ephedrine, etc.) · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
- Tricyclic antidepressants · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
- High tyramine foods (fish, poultry) · Concurrent use not recommended due to MAO inhibition; dangerous hypertension could occur.
Monitoreo
- Efficacy (stool exams for parasitic infections)
Sobredosis
Moderate overdoses are unlikely to cause significant toxicity. Gut emptying may be considered for large overdoses.
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