The main active ingredient is nitrofurantoin.

Common presentations in the UK include 50 mg tablets and 100 mg formulations, with 100 mg modified-release products also available. Nitrofurantoin is an oral antibiotic mainly reserved for infections confined to the lower urinary tract because it concentrates in urine.

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When clinicians choose nitrofurantoin

Nitrofurantoin is typically prescribed for uncomplicated cystitis (bladder infection) caused by organisms that are susceptible to it. Because the drug achieves high concentrations in urine but low levels in blood and tissues, it is not appropriate for kidney infections, prostatitis, or systemic infections that have spread beyond the urinary tract.

Patients with recurrent infections, unusual symptoms, or complex medical histories may be asked to provide a urine sample for culture and sensitivity testing before a longer course or an an optional path antibiotic is recommended. See a different path antibiotics and comparisons for other options commonly used in the UK.

Means of action in the urinary tract

After oral administration nitrofurantoin is rapidly eliminated via the kidneys and concentrated in the urine. There it damages bacterial enzyme systems and microbial DNA, inhibiting growth or killing susceptible bacteria. Because systemic concentrations remain low, its activity is mainly limited to organisms in the bladder and urinary tract.

Dosing advice and practical points

Comply with the exact directives your prescriber provided. General practical tips include the following.

  • Always complete the prescribed course even if symptoms settle earlier.
  • Take doses with food or a light snack to reduce the chance of stomach upset and to aid absorption.
  • Stay well hydrated unless your clinician gives different instructions.
  • Avoid products that contain magnesium trisilicate unless a pharmacist confirms they are safe to use while taking nitrofurantoin.

Patients on long-term prophylactic nitrofurantoin may need periodic checks of kidney, liver and lung function. For what to do about i failed to take my doses, see if you miss a dose.

If you miss one of your doses: simple guidance

  • If you remember shortly after the scheduled time, take the not taking the dose as soon as you recall.
  • If the next dose is due soon, skip the skipped dose and continue with your regular schedule; do not take a double dose to catch up.
  • When in doubt about timing or safety, contact your prescriber or a pharmacist for personalised advice.

Cold keeping materials in storage ensures their availability for future operations. safety and handling

  • Keep at normal room temperature, typically between 15 and 30 degrees C (59 and 86 degrees F).
  • Protect from strong heat, damp and direct sunlight; avoid storing medicines in bathrooms.
  • Store all medicines out of sight and reach of children and pets.

Potential interplays with other medicines

Some agents can affect nitrofurantoin absorption or elimination. Examples worth noting include:

  • Probenecid therapy and sulfinpyrazone, which can reduce renal excretion and raise systemic levels.
  • Antacids containing magnesium trisilicate, which may reduce nitrofurantoin absorption from the gut.

Tell your healthcare team about all prescription medicines, over-the-counter remedies, vitamins and herbal products before starting nitrofurantoin. If you take multiple medicines, ask for a medication review from a pharmacist or prescriber.

UK alerts of potential danger, recommended precautions and clinical circumstances that negate use

No exception contraindication list

  • Known allergy to nitrofurantoin or any excipient in the product.
  • Near term pregnancy (around 38 to 42 weeks), during labour or when labour is imminent.
  • Severe renal impairment or very low urine output.
  • History of severe hepatic reaction linked to previous nitrofurantoin use.
  • Infants in the early weeks of life.

Tell your clinician if you have

  • Pregnant, aiming to conceive, or currently breastfeeding.
  • A history of drug allergies or adverse reactions.
  • Conditions such as anemia, diabetes, porphyria, neuropathy, or chronic kidney or liver disease.
  • Previous lung disease such as interstitial pneumonitis or pulmonary fibrosis.
  • Marked frailty or significant overall poor health.

Other important safety notes and cautionary measures

  • Some people may experience drowsiness or dizziness; avoid driving or operating machinery until you know how nitrofurantoin affects you.
  • Rare, but not trivial. pulmonary reactions have been reported, especially with long-term use. Seek urgent assessment for new fever, persistent cough, chest pain or breathlessness.
  • Severe liver injury is uncommon but possible. Contact a clinician urgently for jaundice, pale stools, dark urine or persistent abdominal pain.
  • Peripheral neuropathy may occur; report new numbness, tingling or burning sensations in the hands or feet promptly, particularly if kidney function is impaired.
  • Antibiotic-associated diarrhea, including Clostridioides difficile infection, can be serious. Seek advice for persistent, severe or bloody diarrhoea.
  • Urine discoloration (yellow to brown) can occur and is usually harmless.
  • Many UK best practice guidance documents advise avoiding nitrofurantoin when estimated glomerular filtration rate (eGFR) is below about 45 mL/min unless a prescriber specifically recommends it.

Possible adverse effects: common reactions and when to seek urgent help

Most patients tolerate nitrofurantoin well. Common, typically mild treatment side effects include:

  • Nausea and mild gastrointestinal discomfort.
  • Cranial pain and reduced appetite.

Ensure you receive urgent medical care for acute problems. any of the following serious signs:

  • Severe allergic reaction: widespread rash, swelling of the face, lips or tongue, difficulty breathing or sudden hoarseness.
  • Severe or bloody diarrhoea, or marked abdominal pain.
  • Indicators of liver injury: yellowing of the skin or eyes, dark urine or pale stools, persistent nausea or severe abdominal pain.
  • Respiratory problems: fever with persistent cough, chest pain or worsening breathlessness.
  • New neurological symptoms: confusion, mood changes, persistent severe severe head pain, or new numbness and tingling.
  • Unexplained bruising, bleeding or extreme tiredness.

The items listed are not a complete set. If you are concerned about any symptom, contact your healthcare provider without delay.

Alternative antibiotics and brief comparisons

Choice of an a different possibility depends on the likely bacteria, local resistance patterns, individual patient factors and kidney function. Frequently offered other options used in the UK for uncomplicated lower urinary tract infection include the following.

  • Trimethoprim — often inexpensive and commonly used where resistance rates are low, but unsuitable in some patients.
  • Fosfomycin trometamol — supplied as a single 3 g sachet for many uncomplicated UTIs; convenient dosing but typically more expensive than nitrofurantoin.
  • Pivmecillinam — a penicillin-type option used in certain settings when other agents are less suitable.
  • Cefalexin — a cephalosporin sometimes chosen in pregnancy or when first-line agents are not appropriate.
  • Amoxicillin or amoxicillin-clavulanate — used only when the causative organism is known to be susceptible due to high resistance rates in many settings.

Discuss the best agent for you with the prescriber. When available, urine culture and sensitivity tests improve the chance of selecting an effective antibiotic.

A UK price estimation guide for shoppers (approximate values in GBP)

Private prices vary between pharmacies and online providers. These are typical ranges and do not include any consultation or delivery fees unless stated.

  • Nitrofurantoin 100 mg modified-release course: roughly 5 to 15 pounds for the medicine alone; online clinics may charge 15 to 35 pounds including assessment fees.
  • Trimethoprim short course: commonly about 1 to 6 pounds privately.
  • Fosfomycin 3 g sachet (single dose): usually 7 to 20 pounds.
  • Pivmecillinam course: typically 8 to 25 pounds depending on supplier.
  • Cefalexin short course: approximately 4 to 12 pounds.

On the NHS most eligible patients pay the standard prescription charge per item; for reference the England NHS prescription charge was 9.90 pounds per item in 2026. Prescriptions are usually free in Scotland, Wales and Northern Ireland for residents. Local Pharmacy First or commissioned schemes may allow pharmacists to supply treatment for uncomplicated female UTIs under agreed rules.

When buying online, factor in any assessment, consultation or delivery costs. Generic versions are usually cheaper than branded products.

Additional aspects about Nitrofurantoin