Disclaimer: This article is for informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.
Overview
Nitrofurantoin is a prescription antibiotic used to treat urinary tract infections that affect the bladder (cystitis). In Canada it is sold as Macrobid, which contains two forms of nitrofurantoin and is taken twice a day, and as nitrofurantoin macrocrystal capsules (originally sold as Macrodantin). Generic versions of both are available.
Nitrofurantoin is concentrated in the urine and reaches only very low levels in the blood. That makes it useful for bladder infections, but it is not a treatment for kidney infections, prostate infections or infections elsewhere in the body. Antibiotics treat bacterial infections only, and they should be used only when a bacterial infection is proven or strongly suspected.
Burning when you pee and needing to go often are common bladder infection symptoms, but they can have other causes. BC residents can speak with a BC-licensed doctor by phone through Avee Health about their symptoms and whether testing or a prescription is needed.
In Canada, Macrobid is authorized for:
- Treatment of acute uncomplicated urinary tract infections, such as cystitis, caused by susceptible strains of E. coli or Staphylococcus saprophyticus, in adults and children over 12
It is not authorized for kidney abscesses, prostatitis or any infection that has spread into the body. Fever, chills, back or side pain, or vomiting with urinary symptoms can mean a kidney infection, which needs a different treatment and prompt medical care.
Nitrofurantoin
Urinary tract antibacterial (nitrofuran antibiotic)
antibiotics
Prescription required
Available
How Nitrofurantoin Works
Bacteria in the urine convert nitrofurantoin into reactive forms that damage several targets at once inside the bacterial cell, including proteins and DNA. This blocks processes the bacteria need to grow and survive.
Because it attacks many targets at the same time, bacteria have rarely become resistant to it since it was introduced in 1953. Most of an absorbed dose passes through the kidneys into the urine, where it reaches levels high enough to stop bacterial growth, while levels in the blood stay low.
Taking it with food can increase how much is absorbed by up to 40% and helps reduce stomach upset.
Dosage Instructions of Nitrofurantoin
Take nitrofurantoin exactly as your prescriber directs. The Canadian Macrobid product monograph gives this usual dose for adults and children over 12:
- One 100 mg capsule every 12 hours, taken with food or milk
- No more than 2 capsules (200 mg) a day
Your prescriber decides how many days to take it. Finish the full course even if you feel better early, and do not share your medicine. If symptoms continue or come back, contact your prescriber, as the infection may need to be re-assessed.
Missed dose: do not take a double dose to make up for a missed capsule. If you are not sure what to do, ask your pharmacist.
Storage Instructions
Store at room temperature, 20°C to 25°C. Keep out of the reach and sight of children.
Side Effects of Nitrofurantoin
In clinical trials of Macrobid, the most common side effects judged possibly or probably related to the medicine were:
- Nausea: 8%
- Headache: 6%
- Gas: 1.5%
Vomiting, diarrhea, stomach pain, dizziness and drowsiness can also occur. Nitrofurantoin can turn urine dark yellow or brown. Vaginal yeast infections can occur, as with other antibiotics.
Stop taking nitrofurantoin and get medical help right away if you have:
- Fever, chills, cough, chest pain or shortness of breath, which can be a lung reaction (sudden reactions usually happen in the first week)
- Yellow skin or eyes, dark urine with itchy skin, or other signs of liver problems
- Numbness or tingling in the hands or feet
- Severe or bloody diarrhea, which can happen during or after antibiotic treatment
- Hives, swelling of the face or mouth, trouble breathing, or a severe rash with blisters or peeling skin
Important Safety Information About Nitrofurantoin
- Kidneys: do not take nitrofurantoin if you have significantly reduced kidney function. It is less effective and more likely to cause side effects in this case.
- Pregnancy: it must not be used during labour and delivery or when labour is close, and should be used during pregnancy only if clearly needed. Tell your prescriber if you are or may be pregnant.
- Babies: it must not be given to infants under 1 month old. Small amounts pass into breast milk, so check with your prescriber before using it while breastfeeding.
- G6PD deficiency: people with this inherited enzyme condition are at risk of a type of anemia caused by nitrofurantoin. Tell your prescriber if you have it.
- Nerves: anemia, diabetes, vitamin B deficiency, abnormal blood salt levels, kidney problems and serious illness raise the risk of nerve damage. Tell your prescriber if any apply to you.
- Long-term use: lung and liver problems are rare but serious, and are more likely with use over several months. People taking it long term need regular check-ups.
- Allergy: do not take it if you are allergic to nitrofurantoin or any ingredient.
Drug Interactions
Tell your prescriber and pharmacist about everything you take, including vitamins and natural products. Known interactions include:
- Antacids containing magnesium trisilicate: reduce how much nitrofurantoin is absorbed
- Gout medicines such as probenecid or sulfinpyrazone: can raise nitrofurantoin levels in the blood and lower them in the urine, making side effects more likely and the treatment less effective
- Medicines that can harm the kidneys: should not be taken with nitrofurantoin
- Quinolone antibiotics, such as ciprofloxacin: the two may work against each other, so they are combined only with caution
- Urine sugar tests: some older urine glucose tests can give a false positive result
Brands & DIN Number of Nitrofurantoin
Brand Names
- Macrobid
- Macrodantin
Key Takeaways
- 1Nitrofurantoin (Macrobid) is a prescription antibiotic used to treat uncomplicated bladder infections (cystitis).
- 2It works in the urine, not the rest of the body, so it is not used for kidney infections or other infections.
- 3The usual Macrobid dose is one 100 mg capsule every 12 hours with food or milk, for the number of days your prescriber sets.
- 4Common side effects are nausea and headache. Dark yellow or brown urine is a known, usually harmless effect.
- 5It is not used in people with significantly reduced kidney function, or near the end of pregnancy.
- 6Stop and get medical help for fever with cough or shortness of breath, yellow skin or eyes, or numbness or tingling.
Frequently Asked Questions
Do I need a prescription for nitrofurantoin in Canada, and how do I get it in BC?
How quickly does nitrofurantoin work for a UTI?
Why is my urine dark yellow or brown on nitrofurantoin?
Can nitrofurantoin treat a kidney infection?
Should I take nitrofurantoin with food?
Can I take nitrofurantoin while pregnant?
How much does nitrofurantoin cost in Canada?
When should I see a doctor for UTI symptoms?
Avee Editorial
Avee Editorial Team