Furazolidone

Synthetic nitrofuran-derivative

Antibacterial / Antiprotozoal (Nitrofuran)POTopicalDogsCatsHorses

Also known as: Furoxone · Enterolidon · Exofur · Furasian · Furion · Furoxona · Fuxol · Giarcid · Giardil · Giarlam · Neo Furasil · Nifuran · Novafur · Salmocide · Seforman · nifurazolidonum

Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference

2.2 mg/kg PO q8hPO· q8h· 7 days

Body weight— 🐕

Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.

Dosing by species

🌎 NA — North America🌍 EU — Europe

Dogs

Indication	Dose	Route	Frequency	Duration	Region
Amebic colitis	2.2 mg/kg PO q8h	PO	q8h	7 days	🌎 NA
Coccidiosis	8-20 mg/kg PO for one week	PO	Unknown	1 week	🌎 NA
Giardia	4 mg/kg PO twice daily (q12h)	PO	q12h	7 days	🌎 NA
Cystoisospora spp.	8-20 mg/kg PO q12-24h	PO	q12-24h	5 days	🌎 NA
Coccidiosis	8-20 mg/kg PO once daily	PO	q24h	7 days	🌎 NA
Entamebiasis	2.2 mg/kg PO q8h	PO	q8h	7 days	🌎 NA

Cats

Indication	Dose	Route	Frequency	Duration	Region
Giardia	4 mg/kg PO twice daily (q12h)	PO	q12h	7-10 days	🌎 NA
Giardia	4 mg/kg, PO twice daily (q12h)	PO	q12h	7 days	🌎 NA
Cystoisospora spp.	8-20 mg/kg PO q12-24h	PO	q12-24h	5 days	🌎 NA
Coccidiosis	8-20 mg/kg PO once daily	PO	q24h	7 days	🌎 NA
Giardiasis	4 mg/kg PO q12h	PO	q12h	5-10 days	🌎 NA
Amebiasis	2.2 mg/kg PO q8h	PO	q8h	7 days	🌎 NA
Amebic colitis	2.2 mg/kg PO q8h	PO	q8h	7 days	🌎 NA
Coccidiosis	8-20 mg/kg PO for one week	PO	Unknown	1 week	🌎 NA
Giardia	4 mg/kg PO q12h	PO	q12h	5 days	🌎 NA

Giardia: If re-treatment is required, elevated dosages or lengthened treatment regimens may provide better results.

Horses

Indication	Dose	Route	Frequency	Duration	Region
Susceptible infections	4 mg/kg PO three times daily	PO	q8h	—	🌎 NA

Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.

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Overview

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.

Mechanism of action

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).

Safety & warnings

Contraindications

Known hypersensitivity to furazolidone or other nitrofurans
Food-producing animals (FDA strictly prohibits extralabel use)
Pregnant queens (per some references)

Adverse effects

Anorexia
Vomiting
Abdominal cramping
Diarrhea
Urine discoloration (dark yellow to brown)

Precautions

Use with extreme caution due to its monoamine oxidase inhibitor (MAOI) properties, which can cause severe interactions with various drugs and tyramine-rich foods. The FDA strictly prohibits the extralabel use of furazolidone in food animals. May cause a false-positive urine glucose determination when using the cupric sulfate solution test (e.g., Clinitest).