Introduction

Nitrofurantoin is a nitrofuran antibiotic used to treat uncomplicated urinary tract infections. Nitrofurantoin is converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein. This drug is more resistant to the development of bacterial resistance because it acts on many targets at once. Nitrofurantoin is a second line treatment to trimethoprim/sulfamethoxazole.

Nitrofurantoin was granted FDA approval on 6 February 1953.

Uses

Nitrofurantoin is an antibiotic used to treat urinary tract infections.

Nitrofurantoin is indicated to treat acute uncomplicated urinary tract infections.

Associated Conditions

Acute Cystitis
Urinary Tract Infection

Pharmacodynamics

Nitrofurantoin interferes with vital processes in bacteria, which leads to their death. Nitrofurantoin rapidly reaches therapeutic concentrations in the urine and is also cleared rapidly.

Mechanism of Action

Nitrofurantoin is converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein.

Absorption

Nitrofurantoin reaches a C_max of 0.875-0.963mg/L with an AUC of 2.21-2.42mg*h/L. It is 38.8-44.3% bioavailable. Taking nitrofurantoin with food increases the absorption and duration of therapeutic concentrations in the urine.

Volume of Distribution

Data regarding the volume of distribution in humans is scarce but it has been reported as 0.46L/kg in dogs.

Protein Binding

Nitrofurantoin could be up to 90% protein bound in plasma.

Route of Elimination

27-50% of an oral dose is excreted in the urine as unchanged nitrofurantoin. 90% of the total dose is eliminated in the urine.

Half Life

The half life of nitrofurantoin is 0.72-0.78h.

Clearance

The clearance of nitrofurantoin is 16.7-19.4L/h.

Toxicity

Symptoms of overdose include vomiting. In case of overdose, induce vomiting if it has not already occurred and increase fluid intake to promote urination. In extreme cases, nitrofurantoin can be removed from circulation by dialysis.

Food Interactions

Take with food. Food decreases irritation and increases bioavailability.

Dosage

Nitrofurantoin tablet (In adults):

Uncomplicated urinary tract infections: 50-100 mg four times a day- the lower dosage level is recommended. Therapy should be continued for one week or for at least 3 days after sterility of the urine is obtained.
For long-term suppressive therapy: In adults, a reduction of dosage to 50-100 mg at bedtime may be adequate.

Nitrofurantoin capsule (In adults):

Acute Uncomplicated Urinary Tract Infections (UTIs): 50 mg four times daily for 7 days.
Long term suppression: 50-100 mg once a day.
Prophylaxis: 50 mg four times daily for the duration of procedure and for three days thereafter.

Nitrofurantoin SR capsule:

Adults and Children over 12 years: One 100 mg capsule every 12 hours for seven days.
Genito-urinary surgical prophylaxis: One capsule twice daily on day of procedure and for next 3 days.

Nitrofurantoin suspension: Children: 5-7 mg/kg/day in four divided doses (contraindicated under one month of age). The average dose of Nintoin suspension for pediatric patients are as follows-

7 to 11 kg: ½ (2.5 ml) teaspoonfuls 4 times daily.
12 to 21 kg: 1 (5 ml) teaspoonfuls 4 times daily.
22 to 30 kg: 1½ (7.5 ml) teaspoonfuls 4 times daily.
31 to 41 kg: 2 (10 ml) teaspoonfuls 4 times daily.

Therapy should be continued for one week or for at least 3 days after sterility of the urine is obtained. For long-term suppressive therapy in children, doses as low as 1 mg/kg per 24 hours, given in a single dose or in two divided doses, may be adequate.

Medical review

Last reviewed: 24 Jul 2026

Medically reviewed by:

This is general information, not personal medical advice. Consult a doctor before taking any medicine.