Loading...
Loading...
Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Nitrofuran Antibacterial [EPC]
Nitrofurantoin is a nitrofuran antibacterial agent primarily used for the treatment and prophylaxis of uncomplicated urinary tract infections (UTIs). It works by interfering with bacterial protein synthesis and metabolism, concentrating specifically in the bladder for targeted efficacy.
Name
Nitrofurantoin
Raw Name
NITROFURANTOIN
Category
Nitrofuran Antibacterial [EPC]
Drug Count
25
Variant Count
207
Last Verified
February 17, 2026
RxCUI
1648755, 311995, 1648759, 311989, 311994, 422434, 201882, 201883, 207791, 539712
UNII
927AH8112L, E1QI2CQQ1I
About Nitrofurantoin
Nitrofurantoin is a nitrofuran antibacterial agent primarily used for the treatment and prophylaxis of uncomplicated urinary tract infections (UTIs). It works by interfering with bacterial protein synthesis and metabolism, concentrating specifically in the bladder for targeted efficacy.
Detailed information about Nitrofurantoin
References used for this content
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Nitrofurantoin.
Nitrofurantoin is a synthetic nitrofuran-derivative antibacterial agent that has been a cornerstone in the management of urinary tract infections (UTIs) for over seven decades. First approved by the U.S. Food and Drug Administration (FDA) in 1953, it remains one of the few antibiotics from that era that maintains high efficacy against common uropathogens (bacteria that cause urinary infections) due to its unique, multi-faceted mechanism of action. Unlike many systemic antibiotics that circulate throughout the entire body, nitrofurantoin is specifically designed to concentrate in the urine, making it a highly localized treatment for bladder infections (cystitis).
Pharmacologically, nitrofurantoin is classified as a nitrofuran antibacterial [EPC]. It is unique because it does not belong to the more common classes like penicillins, cephalosporins, or fluoroquinolones. This distinction is clinically significant because bacteria that have developed resistance to other antibiotic classes often remain susceptible to nitrofurantoin. Healthcare providers frequently utilize this medication as a first-line defense for uncomplicated UTIs, particularly in an era of increasing multi-drug resistant organisms.
To understand how nitrofurantoin works, one must look at its activity at the molecular level. Nitrofurantoin is a 'prodrug,' meaning it is converted into its active form inside the bacterial cell. Bacterial enzymes known as flavoproteins (specifically nitroreductases) reduce the nitrofurantoin molecule into highly reactive electrophilic intermediates. These reactive intermediates are essentially 'molecular wrecking balls' that attack multiple targets within the bacterial cell simultaneously.
These targets include:
Because nitrofurantoin attacks so many different bacterial processes at once, it is very difficult for bacteria to develop resistance through a single genetic mutation. This explains why resistance rates to nitrofurantoin have remained remarkably low despite decades of widespread use. It is primarily bactericidal (kills bacteria) in the urine at therapeutic doses.
Understanding the pharmacokinetics (how the body processes the drug) of nitrofurantoin is essential for optimizing its clinical use.
Nitrofurantoin is rapidly and well-absorbed from the gastrointestinal tract. However, its absorption is significantly influenced by the specific formulation used. There are two main forms: macrocrystals (larger crystals) and monohydrate/macrocrystals. The monohydrate form (often found in the brand Macrobid) creates a gel-like matrix that releases the drug slowly over time, allowing for twice-daily dosing. A critical clinical pearl is that food increases the bioavailability of nitrofurantoin by up to 40%. Taking the medication with a meal not only improves absorption but also minimizes gastrointestinal side effects.
Nitrofurantoin does not achieve high concentrations in the blood or systemic tissues. Instead, it is rapidly cleared from the plasma and concentrated in the urine. This is why it is highly effective for bladder infections but ineffective for systemic infections (sepsis) or kidney infections (pyelonephritis), where higher tissue concentrations are required. It does cross the placenta and is excreted in breast milk in small amounts.
Unlike many drugs that are metabolized by the cytochrome P450 system in the liver, nitrofurantoin is primarily metabolized by the tissues themselves. Approximately 60% of the drug is rapidly metabolized into inactive metabolites, while the remaining 40% is excreted unchanged in the urine.
Nitrofurantoin has a very short elimination half-life of approximately 20 to 60 minutes. It is excreted primarily through the kidneys via glomerular filtration and tubular secretion. Because the drug's efficacy depends on its concentration in the urine, adequate kidney function is required. If the glomerular filtration rate (GFR) is too low, the drug will not reach therapeutic levels in the bladder and may instead accumulate in the blood, increasing the risk of toxicity.
Nitrofurantoin is FDA-approved for the following indications:
While not its primary use, some clinicians may use it off-label for the prevention of UTIs following specific urological procedures, though this is less common than standard prophylactic use.
Nitrofurantoin is available in several oral formulations designed to meet different patient needs:
> Important: Only your healthcare provider can determine if Nitrofurantoin is right for your specific condition. The choice of formulation and dosing schedule depends on the severity of the infection and individual patient factors.
Dosage for nitrofurantoin varies significantly based on whether it is being used for active treatment or long-term prevention. Healthcare providers typically follow these standard guidelines:
Nitrofurantoin is approved for use in pediatric patients older than one month of age. It is contraindicated in infants under one month old due to the risk of hemolytic anemia.
Renal function is the most critical factor in nitrofurantoin dosing. Historically, the FDA label stated the drug was contraindicated in patients with a Creatinine Clearance (CrCl) of less than 60 mL/min. However, recent clinical data and guidelines from the American Geriatrics Society (Beers Criteria) suggest that nitrofurantoin may be used safely and effectively in patients with a CrCl as low as 30 mL/min for short-term treatment of UTIs. If CrCl is below 30 mL/min, the drug is generally avoided as it will not reach effective levels in the urine.
No specific dosage adjustments are provided for patients with hepatic (liver) impairment; however, nitrofurantoin should be used with extreme caution in those with a history of nitrofurantoin-induced liver injury.
Elderly patients are at a higher risk for both pulmonary and hepatic toxicity, especially with long-term use. Healthcare providers must carefully monitor renal function in this population, as age-related decline in GFR may make the drug less effective or more toxic.
To ensure maximum efficacy and safety, patients should follow these instructions:
If you miss a dose, take it as soon as you remember. If it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not 'double up' or take two doses at once to make up for a missed one.
Symptoms of a nitrofurantoin overdose may include severe nausea and vomiting. In the event of an overdose, contact a poison control center or seek emergency medical attention immediately. Because the drug is cleared by the kidneys, maintaining high fluid intake (forced diuresis) may help remove the drug from the system.
> Important: Follow your healthcare provider's dosing instructions precisely. Do not adjust your dose or stop the medication without medical guidance, as this may lead to treatment failure.
The most frequently reported side effects of nitrofurantoin involve the gastrointestinal system. These are typically mild and often resolve once the medication is finished.
> Warning: Stop taking Nitrofurantoin and call your doctor immediately if you experience any of the following serious symptoms:
Nitrofurantoin can cause severe lung reactions.
Nitrofurantoin can cause hepatitis, cholestatic jaundice, and hepatic necrosis. Watch for yellowing of the skin or eyes (jaundice), dark urine (distinct from the drug's normal color change), pale stools, and severe right-sided abdominal pain.
This is a condition where the nerves in the extremities are damaged. It is more common in patients with kidney impairment or diabetes. Symptoms include tingling, numbness, or a 'pins and needles' sensation in the hands or feet. This can become permanent if the drug is not stopped.
In patients with a genetic condition called G6PD deficiency, nitrofurantoin can cause the red blood cells to break down. Symptoms include extreme fatigue, pale skin, and shortness of breath.
When taken for long-term prophylaxis (prevention), the risks of nitrofurantoin change. The primary concern with long-term use is the development of chronic pulmonary fibrosis and chronic active hepatitis. Patients on long-term therapy must have their lung and liver function monitored regularly by their healthcare provider. Long-term use is also associated with an increased risk of peripheral neuropathy, particularly in the elderly.
Currently, the FDA has not issued a formal 'Black Box Warning' for nitrofurantoin. However, the manufacturer's labeling contains 'Bolded Warnings' regarding pulmonary toxicity and hepatotoxicity, which are treated with the same level of clinical gravity as a black box warning. Healthcare providers are instructed to monitor patients closely for any signs of respiratory or hepatic distress.
Report any unusual symptoms or persistent side effects to your healthcare provider immediately. Early detection of serious side effects is crucial for preventing long-term damage.
Nitrofurantoin is a potent antibacterial that requires careful monitoring. It is not a 'general purpose' antibiotic and should only be used for its specifically approved indications. Patients should be aware that this medication will not treat viral infections like the common cold or flu. Overuse of antibiotics can lead to decreased effectiveness for future infections.
No FDA black box warnings for Nitrofurantoin. However, the labeling includes significant warnings regarding pulmonary and hepatic toxicity that must be strictly observed.
Pulmonary reactions (acute, subacute, or chronic) are among the most serious risks associated with nitrofurantoin. Acute reactions are often misdiagnosed as pneumonia or pulmonary edema. If you develop a new cough or difficulty breathing, the drug must be stopped immediately. Chronic reactions are insidious and may develop without obvious symptoms for months; they are often associated with long-term (6 months or more) prophylactic use.
Hepatic reactions, including hepatitis and cholestatic jaundice, have occurred. Some cases have been fatal. Liver function should be monitored, and the drug should be discontinued if signs of liver inflammation appear. These reactions can occur at any time during therapy but are more common with prolonged use.
Severe, and sometimes irreversible, peripheral neuropathy may occur. This risk is significantly higher in patients with renal impairment (CrCl < 60 mL/min), anemia, diabetes mellitus, electrolyte imbalance, or vitamin B deficiency. The first sign is often a tingling sensation in the extremities.
Like almost all antibiotics, nitrofurantoin can alter the natural flora of the colon, leading to an overgrowth of C. difficile. This can cause diarrhea ranging from mild to fatal colitis. If you develop watery or bloody diarrhea, even weeks after stopping the drug, contact your doctor.
Nitrofurantoin may cause hemolytic anemia (the destruction of red blood cells) in patients with Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency. This is a genetic condition more common in people of African, Mediterranean, or South Asian descent.
If you are taking nitrofurantoin for a short course (5-7 days), extensive monitoring may not be required. However, for long-term use, your doctor will likely order:
Nitrofurantoin generally does not cause significant impairment. However, because dizziness and headaches are possible side effects, you should see how you react to the medication before driving or operating heavy machinery.
There is no direct contraindication between alcohol and nitrofurantoin. However, alcohol can irritate the bladder and dehydrate the body, which may worsen UTI symptoms and potentially increase the risk of dizziness or nausea associated with the medication.
There is no 'withdrawal syndrome' associated with stopping nitrofurantoin. However, stopping the drug before the bacterial infection is fully cleared can lead to a 'rebound' infection that is harder to treat. Always finish the prescribed course unless a serious side effect occurs.
> Important: Discuss all your medical conditions, especially lung, liver, or kidney disease, with your healthcare provider before starting Nitrofurantoin.
Nitrofurantoin can cause 'false positive' results in certain diagnostic tests:
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. A complete medication review is the best way to prevent dangerous drug interactions.
Nitrofurantoin must NEVER be used in the following circumstances:
Conditions requiring careful risk-benefit analysis include:
There is a potential for cross-sensitivity among the nitrofuran class of drugs. If a patient has had a severe reaction to furazolidone or nitrofurazone, they should avoid nitrofurantoin. There is no known cross-sensitivity between nitrofurantoin and common antibiotic classes like penicillins or sulfonamides.
> Important: Your healthcare provider will evaluate your complete medical history, including your kidney function and pregnancy status, before prescribing Nitrofurantoin.
Nitrofurantoin is generally classified as FDA Pregnancy Category B. This means that animal studies have failed to demonstrate a risk to the fetus, and there are no adequate, well-controlled studies in pregnant women.
Nitrofurantoin is excreted in human milk in very small amounts. The American Academy of Pediatrics (AAP) considers nitrofurantoin to be generally compatible with breastfeeding. However, it should be avoided if the nursing infant has a known G6PD deficiency or is less than one month old.
Nitrofurantoin is safe and effective for children older than one month. It is commonly used for both the treatment of acute infections and for long-term prophylaxis in children with vesicoureteral reflux (a condition where urine flows backward from the bladder to the kidneys). The oral suspension (Furadantin) is the preferred form for younger children to ensure accurate weight-based dosing.
Elderly patients (65 and older) require special caution.
In patients with moderate renal impairment (CrCl 30-60 mL/min), nitrofurantoin may still be used for short-term UTI treatment (5 days). However, it should not be used for long-term prevention in these patients. For those with CrCl < 30 mL/min, the drug is ineffective and potentially dangerous.
Nitrofurantoin should be used with caution in patients with pre-existing liver disease. While the liver is not the primary site of clearance, the drug's potential for causing drug-induced liver injury (DILI) means that those with already compromised liver function have less 'reserve' if a reaction occurs.
> Important: Special populations, particularly pregnant women and the elderly, require individualized medical assessment and frequent monitoring while taking Nitrofurantoin.
Nitrofurantoin's mechanism is complex and multi-targeted. It is reduced by bacterial flavoproteins (nitroreductases) to reactive intermediates. These intermediates are highly unstable and bind to bacterial ribosomal proteins, DNA, RNA, and enzymes involved in the citric acid cycle. This 'shotgun approach' disrupts the bacteria's ability to create energy, build cell walls, and replicate its genetic material. This is why nitrofurantoin is effective against both Gram-positive and Gram-negative bacteria and why resistance is so rare.
Nitrofurantoin is a concentration-dependent antibiotic with a significant post-antibiotic effect (PAE) against some organisms. Its activity is highest in acidic urine (pH < 5.5). If the urine is highly alkaline, the antibacterial activity of nitrofurantoin is significantly diminished. The drug is primarily bactericidal in the urine at concentrations achieved with standard dosing (approx. 50-200 mcg/mL).
| Parameter | Value |
|---|---|
| Bioavailability | 80% (Increased by food) |
| Protein Binding | 60% to 90% |
| Half-life | 20 to 60 minutes |
| Tmax | 2 hours (Macrocrystals) |
| Metabolism | 60% Hepatic/Tissue metabolism |
| Excretion | Renal (40% unchanged) |
Nitrofurantoin belongs to the Nitrofuran class of antibacterials. Other drugs in this class include furazolidone (used for GI infections) and nitrofurazone (used topically for burns). Nitrofurantoin is the only member of this class used systemically for urinary tract infections in the United States. It is often grouped with 'urinary tract antiseptics' because its therapeutic action is limited to the urinary tract.
Medications containing this ingredient
Common questions about Nitrofurantoin
Nitrofurantoin is primarily used to treat and prevent uncomplicated urinary tract infections (UTIs), commonly known as bladder infections. It is effective against a variety of bacteria, including E. coli, which is the most common cause of UTIs. Because the drug concentrates specifically in the urine rather than the bloodstream, it is not used for kidney infections or systemic infections. Healthcare providers often choose it as a first-line treatment for simple bladder infections because it has low rates of bacterial resistance. It can also be used in low doses over a long period to prevent infections in people who get UTIs frequently.
The most common side effects are gastrointestinal, including nausea, vomiting, and loss of appetite. These symptoms can often be managed by taking the medication with food or milk, which also helps the body absorb the drug better. Another very common but harmless side effect is that the medication will turn your urine a dark yellow or brownish color. Some patients may also experience mild headaches or dizziness. If you experience more severe symptoms like shortness of breath or yellowing of the skin, you should contact your doctor immediately.
While there is no known direct interaction between alcohol and nitrofurantoin that makes the drug dangerous, it is generally advised to avoid alcohol while fighting an infection. Alcohol can irritate the bladder and act as a diuretic, which may worsen the symptoms of a UTI and slow down your recovery. Furthermore, both alcohol and nitrofurantoin can cause stomach upset and dizziness, so combining them may increase the severity of these side effects. It is best to stay hydrated with water and avoid alcohol until you have finished your course of antibiotics and your symptoms have cleared. Always check with your healthcare provider for personalized advice.
Nitrofurantoin is generally considered safe during the first and second trimesters of pregnancy and is a common choice for treating UTIs in pregnant women. However, it is strictly contraindicated (should not be used) during the final weeks of pregnancy (38-42 weeks) and during labor. This is because the drug can cause a serious blood condition called hemolytic anemia in the newborn baby. If you are pregnant, your doctor will weigh the benefits and risks and may choose a different antibiotic if you are close to your due date. Always inform your healthcare provider about your pregnancy status before starting this medication.
Most patients begin to feel relief from their UTI symptoms, such as burning and frequency, within 24 to 48 hours of starting nitrofurantoin. However, even if you feel completely better, it is vital to finish the entire 5-to-7-day course as prescribed. Stopping the medication early can allow the remaining bacteria to survive and multiply, leading to a return of the infection that may be harder to treat. If your symptoms do not improve at all after three days of treatment, you should contact your healthcare provider, as the bacteria causing your infection might be resistant to this specific antibiotic.
You should not stop taking nitrofurantoin suddenly unless you are experiencing a serious allergic reaction or a severe side effect like difficulty breathing. If you stop the antibiotic too early because you feel better, the infection may not be fully cleared, which increases the risk of the UTI returning or the bacteria developing resistance to the drug. If you are experiencing bothersome but mild side effects like nausea, try taking the dose with a larger meal before deciding to stop. Always consult your healthcare provider before discontinuing any antibiotic treatment prematurely.
If you miss a dose of nitrofurantoin, take it as soon as you remember, provided it is not almost time for your next scheduled dose. If it is close to the time for your next dose, simply skip the missed one and continue with your regular schedule. Never take two doses at the same time to make up for a missed one, as this can increase the risk of side effects like nausea and vomiting. To help you remember your doses, try taking the medication at the same time every day, such as with breakfast and dinner. Consistency is key to maintaining enough medicine in your urine to kill the bacteria.
Weight gain is not a known or reported side effect of nitrofurantoin. In fact, because the drug can cause nausea and a loss of appetite in some people, it is more likely to cause temporary weight loss if side effects are significant. If you notice rapid weight gain or swelling (edema) while taking this medication, it could be a sign of a different medical issue or a rare reaction affecting your heart or kidneys, and you should notify your doctor. Always discuss any unexpected changes in your weight with a healthcare professional.
Nitrofurantoin can interact with several other medications, so it is important to provide your doctor with a full list of what you are taking. Specifically, antacids containing magnesium trisilicate can prevent nitrofurantoin from being absorbed properly, and gout medications like probenecid can cause the drug to build up to toxic levels in your blood. It can also interfere with the effectiveness of certain live vaccines, like the oral typhoid vaccine. Most common medications, like birth control pills or blood pressure meds, are generally safe to take with nitrofurantoin, but your pharmacist should always double-check for potential interactions.
Yes, nitrofurantoin is widely available as a generic medication in both the macrocrystal and monohydrate/macrocrystal formulations. Generic versions are typically much more affordable than brand-name versions like Macrobid or Macrodantin and are required by the FDA to have the same quality, strength, and purity. Because it is an older drug, the generic versions have been on the market for many years and are considered highly reliable. Most insurance plans cover generic nitrofurantoin as a low-cost 'Tier 1' medication for the treatment of urinary tract infections.