Nitrofurantoin

Nitrofurantoin is an antibiotic.

It's used to treat water infections, including cystitis and kidney infections.

When you take nitrofurantoin, your body quickly filters it out of your blood and into your pee. This is useful if you have a water infection because it means the medicine is concentrated at the site of infection. But it means nitrofurantoin won't work for any other types of infection.

Nitrofurantoin is available on prescription as capsules, tablets and a liquid that you drink.

  1. Key facts

    • The most common side effect of nitrofurantoin is an upset stomach. Taking this medicine with or straight after food will help prevent a stomach upset.
    • You'll feel better within a few days for most infections.
    • You can drink alcohol while taking nitrofurantoin.
    • Nitrofurantoin may turn pee dark yellow or brown. This is quite normal. Pee will return to normal after you finish taking the medicine.
    • Nitrofurantoin is also called by the brand names Aratoin, Macrobid, Macrodantin and Furadantin.
  2. Who can take nitrofurantoin

    Nitrofurantoin can be taken by adults including pregnant and breastfeeding women.

    Nitrofurantoin isn't suitable for everyone. To make sure it's safe for you, tell your doctor if you have:

    • ever had an allergic reaction to nitrofurantoin
    • either of the rare inherited conditions: porphyria (a blood disorder) or glucose-6-phosphate dehydrogenase (G6PD) deficiency
    • severe kidney disease
    • diabetes
    • any illness causing severe weakness
    • anaemia or vitamin B deficiency
  3. How and when to take

    The usual dose of nitrofurantoin to treat a water infection is either 100mg taken twice a day or 50mg taken 4 times a day. Severe infections may need a higher dose of 100mg taken 4 times a day.

    The usual dose of nitrofurantoin to prevent a water infection is 50mg to 100mg once a day at night.

    Try to space your doses evenly throughout the day. If you're taking nitrofurantoin twice a day, leave 12 hours between each dose – for example, at 8am and 8pm. If you're taking it 4 times a day, this will usually be first thing in the morning, at about midday, late in the afternoon, and at bedtime.

    Generally, it's better to take nitrofurantoin with or after a meal or snack. This helps prevent a stomach upset.

    Carry on taking this medicine until the course is completed, even if you feel better. If you stop your treatment early, your problem could come back.

    How to take it

    Swallow nitrofurantoin tablets and capsules whole. Don't chew or break them.

    There's a liquid nitrofurantoin for people who find it difficult to swallow tablets.

    If you're taking nitrofurantoin as a liquid, it'll usually be made up for you by your pharmacist. The medicine will come with a syringe or spoon to help you take the right amount. If you don't have a syringe or spoon, ask your pharmacist for one.

    The dose of nitrofurantoin you need to take depends on whether it's being used to treat or prevent a water infection, your age, and how bad the infection is.

    How long will I take it for?

    If you're taking nitrofurantoin to treat a water infection, then you usually need to take it for 3 to 7 days.

    If you're taking nitrofurantoin to stop water infections coming back, you may need to take it for several months.

    If you're taking nitrofurantoin to prevent an infection before having surgery, you'll usually need take it on the day of the operation and for the next 3 days.

    What if I forget to take it?

    If you forget to take a dose, take one as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.

    Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

    If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways that are suitable for you and your medicines.

    What if I take too much?

    Taking an extra dose of nitrofurantoin by accident is unlikely to harm you.

    Talk to your pharmacist or doctor if:

    • you're worried or get severe side effects
    • you've taken more than one extra dose
  4. Side effects

    Like all medicines, nitrofurantoin can cause side effects, although not everyone gets them.

    Common side effects

    These common side effects of nitrofurantoin happen in more than 1 in 100 people. Keep taking the medicine, but tell your doctor if they bother you or don't go away:

    • feeling sick and vomiting
    • diarrhoea
    • loss of appetite
    • headaches
    • dizziness or feeling sleepy

    Nitrofurantoin may cause your pee to turn dark yellow or a brownish colour. This is normal and not a reason to stop taking the medicine. Your pee will return to normal once you stop taking nitrofurantoin.

    Serious side effects

    Serious side effects are rare and happen in less than 1 in 1,000 people.

    Tell a doctor straight away if you get:

    • chest pains, difficulty breathing, coughing, chills, or a high temperature (38C or above)
    • yellowing of the skin and/or eyes (warning signs of liver or gallbladder problems)
    • pins and needles, tingling sensations, numbness or weakness (warning signs of nerve problems)
    • bruising or bleeding you can't explain (including nosebleeds), sore throat, a high temperature (38C or above) and feeling tired or generally unwell (warning signs of blood problems)
    • bad headaches

    Serious allergic reaction

    The warning signs of a serious allergic reaction are:

    • difficulty breathing
    • swelling of the face, lips or throat
    • severe skin reactions, including large fluid-filled blisters, sores and ulcers
    • ulcers in the throat and mouth

    A serious allergic reaction is an emergency. Contact a doctor straight away if you think you or someone around you is having a serious allergic reaction.

    These aren't all the side effects of nitrofurantoin. For a full list, see the leaflet inside your medicine packet.

  5. How to cope with side effects

    What to do about:

    • feeling sick – take nitrofurantoin with or after a meal or snack. It may also help if you avoid rich or spicy food.
    • diarrhoea and vomiting – drink plenty of water or other fluids. You may also consider taking oral rehydration solutions you can buy from a pharmacy to prevent dehydration. Don't take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor.
    • headaches – make sure you rest and drink plenty of fluids. Don't drink too much alcohol. Painkillers you can buy without a prescription, such as paracetamol and ibuprofen, are safe to take with nitrofurantoin. Speak to your doctor if these don't help with the headaches or the headaches are severe.

    You can report any suspected side effect to a UK safety scheme.

  6. Pregnancy and breastfeeding

    Nitrofurantoin is generally safe to take during pregnancy and while breastfeeding.

    It's very unlikely that nitrofurantoin is harmful during pregnancy. It goes straight into your pee, so very little of the medicine passes through to the unborn baby. But don't take nitrofurantoin during labour and childbirth, as there's a chance of it affecting the baby's blood.

    Tell your doctor before taking nitrofurantoin if you're breastfeeding. Although it's generally safe to take this medicine while breastfeeding, it may not be suitable for all breastfed babies.  

    Don't take nitrofurantoin while breastfeeding if your baby has a rare condition called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

    For safety, tell your doctor if you're pregnant or breastfeeding before taking nitrofurantoin.

  7. Cautions with other medicines

    There are some medicines that don't mix well with nitrofurantoin. Tell your doctor if you're taking these medicines before you start nitrofurantoin treatment:

    • indigestion remedies known as antacids, particularly those that contain magnesium
    • certain medicines for gout, including probenecid or sulfinpyrazone
    • cystitis remedies you can buy from a pharmacy
    • antibiotics known as quinolones, including nalidixic acid, ciprofloxacin, levofloxacin, norfloxacin, ofloxacin and moxifloxacin

    Typhoid vaccine given by mouth may not work properly if you're taking nitrofurantoin. This doesn't apply to typhoid vaccines given by injection.

    Mixing nitrofurantoin with herbal remedies and supplements

    There are no known problems with taking herbal remedies and supplements with nitrofurantoin.

    However, for safety, speak to your pharmacist before taking nitrofurantoin if you take any herbal or alternative remedies.

  8. Common questions