Who can take nitrofurantoin
Most adults can take nitrofurantoin, including during pregnancy and breastfeeding. Most children can also take it.
Who may not be able to take nitrofurantoin
Nitrofurantoin is not suitable for some people. To make sure it's safe for you, tell your doctor if you have:
- ever had an allergic reaction to nitrofurantoin or any other medicine
- porphyria, a rare blood disorder
- glucose-6-phosphate dehydrogenase (G6PD) deficiency, a rare condition that affects your red blood cells
- severe kidney disease
- a lung condition
- problems with your liver
- any condition causing severe weakness
- anaemia or vitamin B deficiency
The dose of nitrofurantoin you take depends on whether it's to treat or prevent a urinary tract infection, your age, and how bad the infection is.
Nitrofurantoin tablets and capsules come as 50mg or 100mg strengths. The slow release capsules are 100mg. The liquid comes as 25mg in 5ml.
The usual adult dose of nitrofurantoin is:
- to treat a urinary tract infection – either 100mg taken as slow release capsules, twice a day, or 50mg taken as standard tablets or capsules, 4 times a day. Severe infections may need a higher dose of 100mg taken as standard tablets or capsules, 4 times a day
- to prevent a urinary tract infection – 50mg to 100mg taken as standard tablets or capsules, once a day at night
Doses are usually lower for children. Your child's doctor will work out the correct dose based on your child's weight or age.
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, take it 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.
Carry on taking this medicine until you finish the course, even if you feel better. If you stop your treatment early, your problem could come back.
Swallow nitrofurantoin tablets or capsules whole with a drink of water. Do not chew or break them.
Nitrofurantoin also comes as a liquid for younger children or people who find it difficult to swallow tablets.
If you're taking nitrofurantoin as a liquid, the medicine will come with a syringe or spoon to help you take the right amount. If you do not have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not measure the right amount.
Take nitrofurantoin with or after a meal or snack. This helps your body absorb the medicine, as well as helping to prevent stomach upset.
How long to take it for
If you're taking nitrofurantoin to:
- treat a urinary tract infection, you usually need to take it for 3 to 7 days
- stop urinary tract infections coming back, you may need to take it for several months
- prevent an infection when having surgery, you'll usually need to take it on the day of the operation and for the next 3 days
If you forget to take it
If you forget to take a dose of nitrofurantoin, take it 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 at the usual time.
Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.
If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.
If you take too much
Taking an extra dose of nitrofurantoin is unlikely to harm you.
You've taken more than your prescribed dose of nitrofurantoin and:
- you're worried or get severe side effects
- you've taken more than 1 extra dose
Go to 111.nhs.uk or call 111
Call 111 if you're asking about a child under the age of 5 years.
If you go to A&E, take the nitrofurantoin box or leaflet inside the packet plus any remaining medicine with you.
Common side effects
There are things you can do to help cope with these common side effects of nitrofurantoin.
Keep taking the medicine, but speak to a doctor if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Nitrofurantoin may cause your pee to turn dark yellow or a brownish colour. This is normal and is not a reason to stop taking the medicine. Your pee will return to its usual colour once you stop taking nitrofurantoin.
Serious side effects
Serious side effects are rare and happen in less than 1 in 1,000 people.
Call a doctor or contact 111 straight away if you have:
- a cough, coughing up blood or mucus, shortness of breath, pain when you breathe or a high temperature – these can be signs of lung problems
- pale poo and dark pee together, or the whites of your eyes turn yellow or your skin turns yellow (this may be less obvious on brown or black skin) – this can be a sign of liver or gallbladder problems
- bruising or bleeding you cannot explain (including nosebleeds), sore throat, a high temperature and feeling tired or generally unwell – these can be signs of blood problems
- severe headaches
Go to 111.nhs.uk or call 111.
- you get chest pain or difficulty breathing – these can be signs of lung problems
- you get pins and needles, tingling sensations, numbness or weakness – these can be signs of nerve problems
In rare cases, it's possible to have a serious allergic reaction to nitrofurantoin (anaphylaxis).
These are not all the side effects of nitrofurantoin. For a full list see the leaflet inside your medicines packet.
Nitrofurantoin and pregnancy
Nitrofurantoin may be taken during pregnancy, but it is generally best avoided in the third trimester because there's a small chance it could cause problems with your baby's red blood cells.
Most babies will not have this problem, but your doctor may recommend a different antibiotic if you are in the third trimester of pregnancy.
Nitrofurantoin and breastfeeding
If your doctor or health visitor says your baby is healthy, you can take nitrofurantoin while breastfeeding.
Nitrofurantoin passes into breast milk in small amounts and is unlikely to cause side effects in your baby. But it's best to take nitrofurantoin only for a short time. If you need to take it for longer than a few weeks, talk to your doctor or pharmacist.
Do not take nitrofurantoin while breastfeeding if your baby has:
- jaundice – signs include yellowing of the whites of the eyes and the skin (this may be less obvious on brown or black skin), dark pee and pale poo
- glucose-6-phosphate dehydrogenase (G6PD) deficiency, a rare condition that affects red blood cells
If your baby is not feeding as well as usual, has a stomach upset, or has oral thrush (a fungal infection in their mouth), or if you have any other concerns about your baby, talk to your doctor, pharmacist, health visitor or midwife.
Nitrofurantoin and fertility
There's no evidence to suggest that taking nitrofurantoin reduces fertility in either men or women.
Cautions with other medicines
There are some medicines that do not mix well with nitrofurantoin.
Tell your doctor if you're taking any of these medicines before you start taking nitrofurantoin:
- indigestion remedies known as antacids, particularly those that contain magnesium
- cystitis remedies you can buy from a pharmacy
- antibiotics known as quinolones, including nalidixic acid, ciprofloxacin, levofloxacin, norfloxacin, ofloxacin and moxifloxacin
Typhoid vaccines given by mouth may not work properly if you're taking nitrofurantoin. It does not affect typhoid vaccines given by injection.
Mixing nitrofurantoin with herbal remedies and supplements
It's not possible to say that complementary medicines or herbal remedies are safe to take with nitrofurantoin. They're not tested in the same way as pharmacy and prescription medicines.
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