FUROXONE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FUROXONE (FUROXONE).

How it works

Furazolidone is a nitrofuran antimicrobial that inhibits bacterial monoamine oxidase and disrupts bacterial DNA synthesis by undergoing reduction by bacterial nitroreductases to reactive intermediates that cause DNA cross-linking and damage.

What the body does with it

Metabolism	Primarily metabolized in the liver via reduction and conjugation; active metabolites are unknown.
Excretion	Primarily renal (approximately 65%) as unchanged drug; biliary/fecal excretion accounts for about 35%.
Half-life	Terminal elimination half-life is approximately 1.5–2 hours; clinically, this supports dosing every 6 hours for sustained antibacterial effect.
Protein binding	Approximately 25% bound to serum albumin.
Volume of Distribution	Approximately 1.1 L/kg; indicates extensive extravascular distribution including into tissues and fluids.
Bioavailability	Oral: approximately 60–70%; absorption is variable and may be affected by food.
Onset of Action	Oral: within 1–2 hours after administration.
Duration of Action	Approximately 6–8 hours; clinical effect is maintained with every 6-hour dosing.

Classification & Brands

Action Class	Nitrofuran & its derivatives
Brand Substitutes	Furachlor 100mg Tablet

Dosing & administration

100 mg orally four times daily

Dosage form	TABLET
Renal impairment	Contraindicated in renal impairment (CrCl < 50 mL/min). No dose adjustment data available for lesser impairment; use with caution.
Liver impairment	Contraindicated in Child-Pugh B and C cirrhosis. Dose adjustment not defined for mild impairment; monitor closely.
Pediatric use	5 mg/kg/day orally divided into four doses for children over 5 years; not recommended under 1 month of age.
Geriatric use	Initiate at 50 mg orally three times daily; titrate cautiously due to increased risk of adverse effects and renal clearance decline.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FUROXONE (FUROXONE).

Breastfeeding	Furoxone is excreted in human milk. M/P ratio not determined. Due to potential for adverse effects in nursing infants, especially hemolysis in G6PD deficiency, avoid use in breastfeeding. Recommend alternative therapy.
Teratogenic Risk	Furoxone (furazolidone) is contraindicated during pregnancy. Animal studies have shown teratogenic effects, and there are no adequate human studies. Risk of fetal harm if administered during pregnancy, particularly in the first trimester. Use only if clearly needed and no safer alternative exists.

Warnings & precautions

■ FDA Black Box Warning

Furazolidone should not be used in patients with known hypersensitivity to nitrofurans, or in infants under 1 month of age due to the risk of hemolytic anemia. Also carries a warning for disulfiram-like reactions when co-administered with alcohol.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to furazolidone or other nitrofurans","Infants less than 1 month of age","Concurrent use of alcohol or alcohol-containing preparations","Concurrent use of medications with MAOI activity or tyramine-rich foods","Pregnancy (relative contraindication; avoid unless potential benefit outweighs risk)"]

Clinical Precautions

Precautions

["May cause hemolytic anemia in glucose-6-phosphate dehydrogenase (G6PD) deficiency","May produce disulfiram-like reactions with alcohol","Monoamine oxidase inhibitor (MAOI) activity: avoid concurrent use of tyramine-containing foods, sympathomimetics, and other MAOIs","Potential for antibacterial resistance with prolonged use","Use caution in patients with renal impairment"]

Clinical Tips & Counseling

Drug interactions

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FUROXONE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FUROXONE (FUROXONE).

How it works

What the body does with it

Metabolism	Primarily metabolized in the liver via reduction and conjugation; active metabolites are unknown.
Excretion	Primarily renal (approximately 65%) as unchanged drug; biliary/fecal excretion accounts for about 35%.
Half-life	Terminal elimination half-life is approximately 1.5–2 hours; clinically, this supports dosing every 6 hours for sustained antibacterial effect.
Protein binding	Approximately 25% bound to serum albumin.
Volume of Distribution	Approximately 1.1 L/kg; indicates extensive extravascular distribution including into tissues and fluids.
Bioavailability	Oral: approximately 60–70%; absorption is variable and may be affected by food.
Onset of Action	Oral: within 1–2 hours after administration.
Duration of Action	Approximately 6–8 hours; clinical effect is maintained with every 6-hour dosing.

Classification & Brands

Action Class	Nitrofuran & its derivatives
Brand Substitutes	Furachlor 100mg Tablet

Dosing & administration

100 mg orally four times daily

Dosage form	TABLET
Renal impairment	Contraindicated in renal impairment (CrCl < 50 mL/min). No dose adjustment data available for lesser impairment; use with caution.
Liver impairment	Contraindicated in Child-Pugh B and C cirrhosis. Dose adjustment not defined for mild impairment; monitor closely.
Pediatric use	5 mg/kg/day orally divided into four doses for children over 5 years; not recommended under 1 month of age.
Geriatric use	Initiate at 50 mg orally three times daily; titrate cautiously due to increased risk of adverse effects and renal clearance decline.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FUROXONE (FUROXONE).

Breastfeeding	Furoxone is excreted in human milk. M/P ratio not determined. Due to potential for adverse effects in nursing infants, especially hemolysis in G6PD deficiency, avoid use in breastfeeding. Recommend alternative therapy.
Teratogenic Risk	Furoxone (furazolidone) is contraindicated during pregnancy. Animal studies have shown teratogenic effects, and there are no adequate human studies. Risk of fetal harm if administered during pregnancy, particularly in the first trimester. Use only if clearly needed and no safer alternative exists.