Nitrofurantoin is an antibiotic used to treat both acute and chronic urinary tract infections (UTIs), including cystitis and other lower urinary tract infections. It works by eliminating bacteria responsible for urinary infections that are sensitive to this medication.
This antibiotic is available in pharmacies as 100 mg capsules under the brand name Macrobid as well as the generic form labeled “nitrofurantoin.” It is available only with a prescription.
Nitrofurantoin should always be taken as prescribed by a healthcare provider. It is important not to stop treatment early, even if symptoms improve quickly, to prevent bacterial resistance. Stopping the medication too soon can make infections harder to treat and may worsen symptoms.
Indications for use
Nitrofurantoin is indicated for the treatment and prevention of uncomplicated lower urinary tract infections (cystitis) caused by bacteria such as:
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Escherichia coli (E. coli);
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Enterococcus faecalis;
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Staphylococcus aureus;
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Klebsiella;
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Enterobacter.
This medication is not indicated for kidney infections (such as pyelonephritis) or systemic infections because it does not reach effective concentrations in kidney tissue or blood.
Which provider to see
People with UTI symptoms should see a primary care provider or a urologist, who is a specialist in diagnosing and treating conditions that affect the urinary system.
Dosing instructions
Nitrofurantoin 100 mg capsules should be taken by mouth with a full glass of water, preferably with food, to help prevent gastrointestinal side effects.
The usual adult dosage depends on the formulation:
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Macrobid (monohydrate/macrocrystals): 100 mg every 12 hours for 7 days, commonly prescribed for uncomplicated cystitis;
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Macrodantin (macrocrystals): 50–100 mg every 6 hours, mainly used for long-term prevention of recurrent UTIs or when Macrobid is not tolerated.
For long-term UTI prevention, the recommended dose is 50–100 mg once a day, preferably at bedtime, for the duration determined by a healthcare provider.
What to do if you miss a dose
If you forget to take a dose of nitrofurantoin, take it as soon as you remember. However, if it’s almost time for your next dose, skip the missed one and continue with your regular schedule. Do not take a double dose to make up for a missed dose.
Nitrofurantoin side effects
The most common side effects of nitrofurantoin include:
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Nausea;
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Vomiting;
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Loss of appetite;
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Diarrhea;
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Stomach pain.
In some cases, nitrofurantoin may cause interstitial pneumonia, which can present with symptoms such as dry cough, wheezing, shortness of breath, or sudden chest pain. If these symptoms occur, contact your doctor immediately.
Seek medical attention right away if you experience watery or bloody diarrhea, fever, chills, extreme tiredness, body aches, dark urine, pale stools, or yellowing of the skin or eyes (jaundice).
Allergic or anaphylactic reactions can also occur. Go to the nearest emergency room if you experience difficulty breathing, chest tightness, a feeling like your throat is closing, swelling of the mouth, tongue, or face, or hives.
Although rare, nitrofurantoin may also cause drug-induced polyneuropathy, megaloblastic anemia, leukopenia, or excessive intestinal gas.
Does nitrofurantoin change the color of you urine?
Nitrofurantoin may cause urine to appear yellow-brown, which is normal. This happens because the capsule contains an orange coating and yellow powder and granules as part of its composition.
However, nitrofurantoin does not cause urine to turn green or red. If you notice either of these colors, consult your doctor to investigate the cause and, if necessary, adjust the treatment.
Contraindications for use
Nitrofurantoin is contraindicated in anyone allergic to nitrofurantoin or its ingredients and should not be prescribed to infants younger than 1 month old. People with significantly reduced kidney function should also avoid taking nitrofurantoin.
Nitrofurantoin should generally not be used during breastfeeding if the infant is younger than 1 month old or has G6PD deficiency, due to the risk of hemolysis. In other cases, short-term use is considered acceptable.
In adults over 65 years of age, nitrofurantoin should be used only if approved by a healthcare provider, as older adults are at greater risk for lung or liver side effects, especially with long-term use.
Nitrofurantoin during pregnancy
People who are pregnant should avoid using nitrofurantoin during the final weeks of pregnancy (weeks 38–42) or during labor and delivery because it may cause hemolytic anemia in the newborn, a condition in which red blood cells are destroyed faster than they are produced.
Use earlier in pregnancy may be considered if benefits outweigh risks and if no safer alternatives are available.