Nitrofurantoin: Uses, dosage, side effects, warnings & patient reviews

What is Nitrofurantoin?

Nitrofurantoin is a prescription antibacterial medication belonging to the nitrofuran class. It is unique among antibiotics because it concentrates specifically in the urine of the bladder, making it highly effective for treating lower urinary tract infections. It is not effective for treating systemic or kidney infections, as it does not achieve adequate concentrations in blood or deep tissues.

The medication is available in two main crystalline formulations designed to improve tolerability: nitrofurantoin monohydrate/macrocrystals (brand name Macrobid) and nitrofurantoin macrocrystals (brand name Macrodantin). These formulations release the drug slowly to minimize stomach upset.

As with all antibiotics, it is crucial to use nitrofurantoin only for bacterial infections confirmed or suspected by a healthcare provider, and to complete the full prescribed course.

How to Take Nitrofurantoin

Following administration instructions precisely improves effectiveness and reduces the risk of gastrointestinal side effects.

Administration and Timing

Take nitrofurantoin capsules with food or milk. This significantly enhances absorption and helps prevent nausea and stomach upset. Swallow the capsule whole with a full glass of water; do not crush, chew, or open it.

Course Completion and Missed Dose

It is essential to complete the entire prescribed course of antibiotics, even if symptoms improve after a few days. Stopping early can lead to a resurgence of the infection and contribute to antibiotic resistance. For general guidance on antibiotic use, see our resource on using antibiotics correctly.

If you miss a dose, take it as soon as you remember with food. If it is almost time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not take two doses at once to make up for a missed dose.

Side Effects of Nitrofurantoin

Like all medications, nitrofurantoin can cause side effects. For a broader understanding of managing medication reactions, you may find our guide on side effects helpful.

What is Nitrofurantoin Used For?

Nitrofurantoin has specific, targeted uses in treating and preventing bacterial infections of the urinary tract.

Primary Medical Uses

• Treatment of Acute Uncomplicated Cystitis: It is a first-line agent for treating acute, uncomplicated bacterial cystitis (bladder infections) in women caused by susceptible strains of E. coli and Staphylococcus saprophyticus.
• Prophylaxis of Recurrent UTIs: It is used long-term at a low dose to prevent frequent recurrences of urinary tract infections.

Important Limitations

Nitrofurantoin is not indicated for the treatment of pyelonephritis (kidney infections) or perinephric abscesses. Due to its pharmacokinetics, it does not achieve therapeutic tissue concentrations in the kidneys or the bloodstream. For suspected kidney infections, systemic antibiotics like ciprofloxacin may be required. It is also ineffective against infections outside the urinary tract.

Treatment decisions, such as choosing between nitrofurantoin and another common UTI antibiotic like Bactrim DS, should be made by a healthcare provider based on the specific bacteria and patient factors.

Important Safety Concerns and Considerations

Pulmonary Reactions

Severe and sometimes fatal pulmonary reactions can occur with nitrofurantoin. These include acute pulmonary hypersensitivity reactions (appearing within hours to days of therapy) and chronic pulmonary reactions (associated with long-term use). Symptoms include dyspnea, cough, fever, chills, and chest pain. The drug should be discontinued immediately if these occur.

Hepatotoxicity

Cases of hepatic toxicity, including hepatitis, cholestatic jaundice, chronic active hepatitis, and hepatic necrosis, have been reported rarely. Fatal outcomes have occurred. Liver function should be monitored periodically with long-term therapy. The drug should be discontinued at the first sign of liver injury.

Peripheral Neuropathy

Peripheral neuropathy, which may become severe or irreversible, has occurred. Risk factors include renal impairment, diabetes mellitus, electrolyte imbalances, anemia, vitamin B deficiency, and debilitating disease. Patients should report symptoms like numbness, tingling, or pain. The drug should be discontinued if neuropathy develops.

Hemolytic Anemia

Nitrofurantoin can cause hemolytic anemia of the primaquine-sensitivity type, linked to a deficiency in the enzyme glucose-6-phosphate dehydrogenase (G6PD). This reaction is dose-related and more common in certain ethnic groups. The drug is contraindicated in patients with known G6PD deficiency.

Clostridioides difficile-Associated Diarrhea (CDAD)

Antibiotic use, including nitrofurantoin, can cause C. difficile-associated diarrhea, which may range from mild to life-threatening colitis. This can occur even months after antibiotic discontinuation. Report severe, persistent, or bloody diarrhea to your doctor.

Critical Warnings for Nitrofurantoin Use

Contraindication in Renal Impairment

Nitrofurantoin is contraindicated in patients with significant renal impairment (a creatinine clearance under 60 mL/min or clinically significant elevated serum creatinine). Ineffective tissue levels are achieved in the urine with poor renal function, and the risk of toxicity increases due to drug accumulation. For more on kidney health, see information on kidney disease.

Acute, Subacute, or Chronic Pulmonary Reactions

As noted in the concerns section, pulmonary reactions are a serious risk. Fatalities have been reported. Patients should be closely monitored for respiratory symptoms. Chronic pulmonary reactions are more common in elderly patients on long-term therapy.

Hepatic Reactions

Fatal hepatic necrosis and other serious hepatotoxic reactions have occurred. Chronic active hepatitis has been reported with long-term therapy. Patients should be monitored, and the drug discontinued if evidence of liver dysfunction appears.

Peripheral Neuropathy Warning

Irreversible peripheral neuropathy can occur. Conditions such as diabetes, renal impairment, anemia, and vitamin B deficiency increase risk. The drug should be used with extreme caution in patients with these conditions and discontinued at the first sign of neuropathy.

Use in Pregnancy at Term

Nitrofurantoin should not be used at term (38-42 weeks gestation) or during labor and delivery, as it may cause hemolytic anemia in the neonate due to immature enzyme systems (glutathione instability).

Nitrofurantoin Dosage Information

Dosage depends on the formulation (Macrobid vs. Macrodantin/Furadantin) and indication (treatment vs. prevention). Always follow your doctor’s prescription.

Important Administration Notes

• Renal Function: Contraindicated if creatinine clearance is under 60 mL/min.
• With Food: Always take with food or milk to improve bioavailability and tolerance.
• Duration: Complete the full prescribed course for treatment. Do not stop early.

Drug Interactions with Nitrofurantoin

Inform your doctor about all medications you are taking, including over-the-counter drugs and supplements.

Additional Information

Storage and Handling

Store nitrofurantoin capsules at room temperature between 20°C and 25°C (68°F and 77°F), in a tightly closed container, away from light, excess heat, and moisture. Keep out of reach of children and pets.

Mechanism of Action

Nitrofurantoin is a unique bacteriostatic antibacterial. It is thought to work by damaging bacterial DNA through the activity of reactive intermediates formed when the drug is reduced by bacterial enzymes. Its selective activity in the urinary tract is due to its rapid absorption, followed by rapid renal excretion and concentration in urine.

Reporting Side Effects

You are encouraged to report negative side effects of prescription drugs to your national health authority (e.g., the FDA in the United States). Reporting helps monitor drug safety and identify new risks.

References and Medical Sources

The information on this page is compiled from reputable medical sources and prescribing information.

1. U.S. Food and Drug Administration (FDA). Macrobid (nitrofurantoin monohydrate/macrocrystals) Prescribing Information. [Updated 2020]. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/020064Orig1s029lbl.pdf
2. MedlinePlus. Nitrofurantoin. U.S. National Library of Medicine; [Updated 2022]. https://medlineplus.gov/druginfo/meds/a682291.html
3. Infectious Diseases Society of America (IDSA). International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update. Clinical Infectious Diseases. 2011.
4. Drugs.com. Nitrofurantoin Professional Monograph. Drugs.com; [Updated 2024]. https://www.drugs.com/monograph/nitrofurantoin.html

Disclaimer: The information on this site is provided for informational purposes only and is not medical advice. It does not replace professional medical consultation, diagnosis, or treatment. Do not self-medicate based on the information presented on this site. Always consult with a doctor or other qualified healthcare professional before making any decisions about your health.