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What Is Nitrofurantoin?

Nitrofurantoin is a prescription antibiotic used to treat certain bacterial urinary tract infections, particularly infections involving the bladder. It is available in several oral formulations, including nitrofurantoin macrocrystals and nitrofurantoin monohydrate/macrocrystals. These products differ in dosing and release characteristics. Nitrofurantoin concentrates in the urine, making it useful against susceptible bacteria in the lower urinary tract. It is not appropriate for every type of urinary tract infection.

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What Is Nitrofurantoin?

Nitrofurantoin is a prescription antibiotic used to treat certain bacterial urinary tract infections, particularly infections involving the bladder. It is available in several oral formulations, including nitrofurantoin macrocrystals and nitrofurantoin monohydrate/macrocrystals. These products differ in dosing and release characteristics. Nitrofurantoin concentrates in the urine, making it useful against susceptible bacteria in the lower urinary tract. It is not appropriate for every type of urinary tract infection.

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How Does Nitrofurantoin Work?

Nitrofurantoin enters susceptible bacterial cells and is converted into reactive compounds by bacterial enzymes. These compounds interfere with several processes involved in bacterial survival, including protein synthesis and the function of genetic material. Nitrofurantoin reaches therapeutic concentrations in the urine but does not achieve adequate tissue levels for treating infections involving the kidneys. This limits its use primarily to lower urinary tract infections.

What Infections Does Nitrofurantoin Treat?

Nitrofurantoin is commonly prescribed for uncomplicated bacterial bladder infections, also called acute cystitis, caused by susceptible organisms. It is active against many strains of Escherichia coli and certain other urinary pathogens, depending on the formulation and susceptibility results. Nitrofurantoin should not be used to treat pyelonephritis, which is a kidney infection, or infections requiring substantial antibiotic concentrations outside the urinary bladder. Fever, flank pain, or systemic illness can indicate the need for a different treatment.

How Should Nitrofurantoin Be Taken?

Nitrofurantoin dosing depends on the formulation. Nitrofurantoin monohydrate/macrocrystals 100 mg is commonly prescribed twice daily for five days for uncomplicated cystitis in adult women, although some product labels specify a seven-day course. Macrocrystal formulations generally follow more frequent dosing schedules. Taking nitrofurantoin with food improves absorption and can reduce stomach discomfort. Complete the prescribed treatment course, and follow the exact instructions on the dispensed product rather than substituting doses between formulations.

What Are the Side Effects and Warnings of Nitrofurantoin?

Common side effects include nausea, headache, abdominal discomfort, and changes in urine color. Serious adverse effects include lung inflammation, peripheral neuropathy, liver injury, and hemolytic anemia in susceptible individuals. Nitrofurantoin is contraindicated in patients with significantly impaired kidney function under product labeling and in pregnancy at term because of the risk of hemolysis in newborns. New breathing difficulties, numbness, or symptoms of liver injury require prompt medical evaluation.

Common Questions About Nitrofurantoin

Does nitrofurantoin treat urinary tract infections?

Yes. Nitrofurantoin is used to treat certain bacterial infections of the lower urinary tract, particularly uncomplicated bladder infections caused by susceptible bacteria.

Can nitrofurantoin treat a kidney infection?

No. Nitrofurantoin does not reach adequate concentrations in kidney tissue to treat pyelonephritis. Kidney infections require other appropriate antibiotics.

Should nitrofurantoin be taken with food?

Yes. Taking nitrofurantoin with food improves absorption and can reduce gastrointestinal side effects.

Can nitrofurantoin change urine color?

Yes. Nitrofurantoin can turn urine dark yellow or brown. This is generally harmless, but other concerning symptoms should be discussed with a clinician.

References

DailyMed - NITROFURANTOIN MONOHYDRATE/MACROCRYSTALS capsule. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=48a128ce-9279-4d39-b1eb-c4d2dd56f701. Date Accessed October 19, 2026.

Nitrofurantoin. LiverTox. https://www.ncbi.nlm.nih.gov/books/NBK548318/. Date Accessed October 19, 2026.

Nitrofurantoin. MedlinePlus. https://medlineplus.gov/druginfo/meds/a682291.html. Date Accessed October 19, 2026.

Nitrofurantoin. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Nitrofurantoin. Date Accessed October 19, 2026.

Nitrofurantoin. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK470526/. Date Accessed October 19, 2026.