Elephant specific information, if available, is in blue.

Chemistry – A synthetic nitrofuran-derivative antibacterial/antiprotozoal, furazolidone occurs as a bitter-tasting, yellow, crystalline powder. It is practically insoluble in water.

Storage/Stability/Compatibility – Store protected from light in tight containers. Do not expose the suspension to excessive heat.

Pharmacology – Furazolidone interferes with susceptible bacterial enzyme systems. Its mechanism against susceptible protozoa is not well determined. Furazolidone has activity against Giardia, Vibrio cholerae, Trichomonas, Coccidia and many strains of E. Coli, Enterobacter, Campylobacter, Salmonella and Shigella. Not all strains are sensitive, but resistance is usually limited and develops slowly. Furazolidone also inhibits monoamine oxidase.

Uses/Indications – Furazolidone is usually a drug of second choice in small animals to treat enteric infections caused by the organisms listed above.

Pharmacokinetics – Conflicting information on furazolidone’s absorption characteristics are published. As colored metabolites are found in the urine, it is clearly absorbed to some extent. Because furazolidone is used to treat enteric infections, absorption becomes important only when discussing adverse reactions and drug interaction issues. Furazolidone is reported to be distributed into the CSF. Absorbed furazolidone is rapidly metabolized in the liver and the majority of absorbed drug is eliminated in the urine.

Contraindications/Precautions/Reproductive Safety – Furazolidone is contraindicated in patients hypersensitive to it. While the safe use of furazolidone during pregnancy has not been established, neither have there been any teratogenic problems reported for the drug. It is unknown if furazolidone enters maternal milk.

Adverse Effects/Warnings – Adverse effects noted with furazolidone are usually minimal. Anorexia, vomiting, cramping and diarrhea may occasionally occur. Some human patients are reported to be hypersensitive to the drug. Because furazolidone also inhibits monoamine oxidase, it may potentially interact with several other drugs and foods (see Drug Interactions below). The clinical significance of these interactions is unclear, particularly in light of the drug’s poor absorptive characteristics.

Overdosage/Acute Toxicity – No information was located; but moderate overdoses are unlikely to cause significant toxicity. Gut emptying may be considered for large over­doses.

Drug Interactions – Because furazolidone inhibits monoamine oxidase, its use concurrently with buspirone, sympathomimetic amines (phenylpropanolamine, ephedrine, etc.), tricyclic antidepressants, other monamine oxidase inhibitors, and fish or poul­try (high tyramine content) is not recommended because dangerous hypertension could occur. Alcohol used concurrently with furazolidone may cause a disulfiram-like reaction.

Laboratory Considerations – Furazolidone may cause a false-positive urine glucose determination when using the cupric sulfate solution test (e.g., Clinitest®).

Doses –

Horses:

a)   4 mg/kg PO tid (Robinson 1992)

Monitoring Parameters – Efficacy (stool exams for parasitic infections)

Client Information – Furazolidone may discolor urine to a dark yellow to brown color; this is not significant. Have clients report prolonged or serious GI effects.

Dosage Forms/Preparations/FDA Approval Status/Withholding Times –

Veterinary-Approved Products: None

Human-Approved Products:

Furazolidone Oral Liquid 3.34 mg/ml (50 mg/15 ml) in 60 ml and pint bottles; Furoxone®  (Procter & Gamble Pharm);(Rx)

Furazolidone Oral Tablets 100 mg; Furoxone®  (Procter & Gamble Pharm); (Rx)