Description
Nitrofurantoin is an antibacterial medicine from the nitrofuran group. It works by:
- Entering bacterial cells and damaging their DNA and other vital processes
- Killing or stopping the growth of many common urinary bacteria
- Reaching high concentrations in the urine, where it acts directly on bacteria in the bladder and lower urinary tract
It is active against many common UTI bacteria such as E. coli, enterococci, some staphylococci, Citrobacter, Klebsiella and Enterobacter species. It does not treat infections caused by resistant organisms like most Proteus, Serratia and all Pseudomonas strains.
Nitrofurantoin only works on bacterial infections – it will not help with viral illnesses (such as colds or flu).
Who it may be suitable for
Nitrofurantoin capsules are used for:
- Treatment of acute uncomplicated lower UTIs (such as cystitis)
- Treatment of recurrent or more severe lower UTIs, where appropriate
- Prevention (prophylaxis) or long-term suppression of recurrent uncomplicated UTIs
- UTIs associated with certain surgical or urological procedures
They may be prescribed for:
- Adults, including older adults (if kidney function is suitable)
- Children and infants over 3 months of age
Who should not take Nitrofurantoin
Do not take nitrofurantoin if you:
- Are allergic to nitrofurantoin, other nitrofurans, or any capsule ingredient
- Have kidney problems with an eGFR < 45 ml/min or significant renal impairment
- Have a known G6PD deficiency (risk of haemolytic anaemia)
- Have acute porphyria
- Are an infant under 3 months of age
- Are pregnant at term, in labour, or your due date is very close, because of the risk of haemolytic anaemia in the newborn
Use with extra care / medical supervision
Extra caution is needed if you:
- Have existing lung disease or breathing problems
- Have liver disease or abnormal liver tests
- Have neurological disorders (e.g. peripheral neuropathy)
- Have anaemia, diabetes, electrolyte imbalance, vitamin B/folate deficiency or other debilitating conditions
- Are elderly, especially if using nitrofurantoin long term
- Have a history of allergies or severe skin reactions
In long-term use, your doctor may arrange regular checks (e.g. lung function and liver tests) and will advise you to report new symptoms such as cough, breathlessness, jaundice or tingling in the hands/feet promptly.
Pregnancy and breastfeeding:
- Nitrofurantoin has been widely used in pregnancy but should be used at the lowest effective dose and avoided at term.
- Small amounts pass into breast milk; breastfeeding should be avoided in infants with suspected enzyme deficiencies (e.g. G6PD).
Side Effects
Like all medicines, nitrofurantoin can cause side effects, although not everyone gets them.
Very common / common side effects:
- Nausea or vomiting
- Loss of appetite
- Abdominal (tummy) pain or discomfort
- Diarrhoea
- Headache or dizziness
- Urine colour change – urine may become yellow or brown (this is harmless)
These are often mild and may improve if you take the capsules with food.
Less common side effects (see a doctor if troublesome):
- Skin rash, itching or hives
- Drowsiness or feeling “spaced out”
- Numbness, tingling or pins and needles in hands or feet (possible nerve irritation)
- Thrush (fungal infection) due to disturbance of normal flora
- Mild abnormal liver tests
Serious side effects – stop the medicine and seek urgent medical help if you notice:
1. Lung (pulmonary) reactions – can be acute, subacute or chronic:
- Sudden breathlessness or difficulty breathing
- Cough, sometimes with mucus or blood
- Chest pain
- Fever, chills, malaise
These may occur within the first week of treatment (acute reaction) or develop gradually with long-term use (chronic reaction, including pulmonary fibrosis).
2. Liver problems (hepatitis, jaundice)
- Yellowing of the skin or eyes
- Dark urine, pale stools
- Persistent nausea, vomiting, tiredness, or upper right abdominal pain
3. Blood disorders
- Unusual bruising or bleeding
- Persistent sore throat, infections, mouth ulcers
- Extreme tiredness, paleness, breathlessness
4. Severe skin reactions / allergy
- Widespread rash, blistering or peeling skin (possible Stevens-Johnson syndrome or DRESS)
- Swelling of face, lips, tongue or throat
- Difficulty breathing or swallowing
- Sudden drop in blood pressure, collapse
5. Nerve damage (peripheral neuropathy)
-
Persistent numbness, burning, tingling or weakness in hands or feet
Stop taking nitrofurantoin and contact a doctor immediately if you develop otherwise unexplained lung, liver, blood or nerve symptoms.
Patient Information Leaflet
Please see HERE for the Patient Information Leaflet
Additional Info
Key facts about Nitrofurantoin 100 mg Capsules:
- Active ingredient: 100 mg nitrofurantoin (macrocrystalline form) per capsule
- Indication: Treatment and prevention of uncomplicated lower urinary tract infections and pyelitis caused by susceptible bacteria
- Not suitable for: Severe kidney impairment (eGFR < 45 ml/min), infants < 3 months, late pregnancy/labour, G6PD deficiency, acute porphyria
- Form: Hard gelatin capsule, usually yellow
- Contains lactose (approx. 207 mg per capsule) – not suitable if you have rare hereditary problems of galactose intolerance, total lactase deficiency or glucose–galactose malabsorption
- Driving and machinery: May cause dizziness or drowsiness – do not drive or operate machinery if affected
- Urine tests: Can cause false-positive results for glucose in urine (reducing substances)
Drug and food interactions:
- Take with food or milk – improves absorption and effectiveness
- Magnesium trisilicate antacids may reduce absorption and effectiveness
- Probenecid and sulfinpyrazone can reduce renal excretion of nitrofurantoin, possibly reducing urinary levels and increasing side effects
- Carbonic anhydrase inhibitors and urine alkalinisers can reduce antibacterial activity
- Quinolone antibiotics (e.g. ciprofloxacin) may antagonise the effect of nitrofurantoin
- As with other antibacterials, nitrofurantoin can inactivate the oral typhoid vaccine
Always tell your prescriber or pharmacist about all other medicines or supplements you are taking.
Directions
Nitrofurantoin 100 mg capsules are for oral use.
- Swallow the capsule whole with water
- Always take it with food or milk – this improves absorption and reduces stomach upset
- Take it exactly as prescribed on your label
Typical adult dosing patterns (your prescription may differ):
- Acute uncomplicated UTI: usually 50–100 mg four times a day for around 7 days
- Severe chronic recurrence: up to 100 mg four times a day for 7 days, as directed
- Long-term suppression / prevention: 50–100 mg once daily, often at bedtime
- Prophylaxis around surgery or procedures: 50 mg four times a day during the procedure period and for roughly 3 days afterwards
For children over 3 months, the dose is based on body weight; your prescriber will specify the amount. For young children or those under 25 kg, an oral suspension is usually preferred rather than capsules.
Important:
- Do not change the dose or stop early unless directed – finish the prescribed course even if you start to feel better
- If you are on long-term treatment, attend regular check-ups as advised
Missed a dose?
If you forget a dose:
- Take it as soon as you remember, with food or milk
- If it is nearly time for your next dose, skip the missed one and take the next at the usual time
- Do not take two doses at the same time to make up for a missed capsule
For people on once-daily or long-term regimens, missing occasional doses may reduce protection against infection. If you miss doses frequently, speak to your prescriber.
If you vomit soon after taking a capsule, the medicine may not have been absorbed – contact a pharmacist or clinician for advice; you may be told to take another dose depending on timing and how unwell you are.
FAQs
What is Nitrofurantoin 100 mg used for?
Nitrofurantoin 100 mg is used to treat or prevent lower urinary tract infections like cystitis caused by sensitive bacteria, but it is not appropriate for kidney infections or resistant organisms.
How quickly will it work for a UTI?
While many people see improvement in burning and frequency within 24 to 48 hours, you must finish the entire prescribed course to ensure the infection is cleared and to prevent resistance or recurrence.
Why do I have to take it with food?
Taking each dose with a meal or snack improves the absorption of the medicine into the urine and helps reduce common side effects like stomach upset, nausea, and vomiting.
Can I use it if I have kidney problems?
No, Nitrofurantoin is generally not used if your eGFR is below 45 ml/min because it may not work effectively in the urine and increases the risk of side effects, so a doctor will check your kidney function before prescribing.
Why has my urine turned dark?
It is harmless and expected for your urine to turn yellow or brown while taking this medication, but you should speak to a clinician if you notice blood in your urine or other worrying changes.
Does Nitrofurantoin interact with alcohol?
There is no direct interaction with alcohol, but it is sensible to limit intake while taking nitrofurantoin to avoid increased stomach upset, drowsiness, or dizziness while you are unwell.
Does it affect the contraceptive pill?
Nitrofurantoin does not directly reduce the effectiveness of the pill, but severe vomiting or diarrhoea can interfere with absorption, requiring you to follow missed pill protocols and use extra protection like condoms.
Can children take Nitrofurantoin capsules?
Nitrofurantoin can be used in children older than 3 months with a weight-based dose, though an oral suspension is often preferred for smaller children, and it must never be used in babies under 3 months old.
What if my symptoms don’t improve or keep coming back?
If symptoms persist after 2 to 3 days or if you develop fever and flank pain, seek medical advice immediately as this may indicate a kidney infection, and recurrent issues may require further investigation.
When should I get urgent help?
Seek urgent medical attention from 24 HR Pharmacy or emergency services if you experience new breathlessness, jaundice, severe blistering rashes, facial swelling, unexplained bruising, or numbness and weakness in your extremities.
What They Say About Us...
Great service, the follow up phone call to ensure that I was getting the correct medication was appreciated. Would yes 24 HR Pharmacy again.
Excellent customer service and prompt communication. My enquiry was resolved quickly, and my order was delivered ahead of time.
The service I received was faultless. Sehar is very knowledgeable and supportive in her consultation. The service was quick and easy to use.