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Nitrofurantoin is a first-line antibiotic for uncomplicated urinary tract infections. It acts specifically in the bladder but is not suitable for impaired kidney function or a kidney infection.
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Take nitrofurantoin for exactly as long as prescribed – even if your symptoms already ease after one or two days. Stopping on your own can let the urinary tract infection return and encourage resistance. Nitrofurantoin (brand names Furadantin®, Nifurantin®) is an antibiotic used specifically for a bladder infection (urinary tract infection). It accumulates almost exclusively in the urine and therefore acts exactly where the bacteria are – in the bladder. Guidelines recommend it as one of the first-line agents for uncomplicated infections.
| Property | Details |
|---|---|
| Active ingredient | Nitrofurantoin |
| Brand name | Furadantin®, Nifurantin® |
| ATC code | J01XE01 |
| Drug class | Urinary tract antibiotic (nitrofuran derivative) |
| Formulation | Extended-release capsules/tablets 50 and 100 mg |
| Intake | With a meal, with plenty of fluid |
| Standard dose | 2× 100 mg/day (extended-release) over 5 days |
| Prescription required | Yes |
| Special note | Not for impaired kidney function; harmless brown discolouration of the urine |
Nitrofurantoin is a so-called urinary tract antibiotic. This means that after intake the active ingredient is barely distributed in the body but is rapidly excreted via the kidneys into the urine. This produces high concentrations exactly where the bacteria sit in a bladder infection – in the urinary bladder. In the blood and the rest of the tissue, by contrast, the level stays low.
Inside the bacterial cell, nitrofurantoin is converted into reactive fragments that attack numerous bacterial building blocks at once – from the genetic information through to proteins and cell metabolism. Because the antibiotic acts at so many points, resistance has remained rare so far. Typical triggers of a urinary tract infection such as E. coli usually respond well to it. This very targeted action in the bladder is also the reason why nitrofurantoin helps well with symptoms such as burning when urinating and a constant urge to urinate – but is not sufficient for a kidney infection, because it barely reaches the kidney tissue.
For an uncomplicated urinary tract infection, the usual choice is the extended-release (slow-release) form with 2× 100 mg daily over five days. Important: nitrofurantoin is always taken with a meal. This improves absorption and is gentler on the stomach.
| Situation | Dose |
|---|---|
| Uncomplicated urinary tract infection (extended-release form) | 2× 100 mg/day over 5 days |
| Non-extended-release form | 3–4× 50–100 mg/day over 5–7 days |
| Impaired kidney function (GFR < 45 ml/min) | Do not use |
| Kidney infection (pyelonephritis) | Not suitable |
A missed dose is made up as soon as you notice it – but if the next dose is already almost due, the missed one is skipped and you never take the double amount. What generally applies to a missed dose is explained in the guide Forgotten your medication.
brite reminds you of every nitrofurantoin dose and documents your course without gaps.
For an uncomplicated urinary tract infection, several antibiotics are available. Nitrofurantoin and fosfomycin are considered first-line agents. Ciprofloxacin from the fluoroquinolone group, by contrast, is explicitly not to be used as standard for a simple bladder infection – it is reserved for more severe infections.
| Property | Nitrofurantoin | Fosfomycin | Ciprofloxacin |
|---|---|---|---|
| Intake | 2× daily over 5 days | Single dose (1 sachet) | 2× daily over 3 days |
| Role in simple infection | First line | First line | Reserve only |
| For kidney infection | No | No | Yes (if needed) |
| For impaired kidney function | No | Limited | Dose adjustment |
| Special note | Acts only in the bladder | Convenient single dose | More side effects, reserve antibiotic |
Which antibiotic is right depends on kidney function, pregnancy, pre-existing conditions and the local resistance pattern. None is universally „the best" – the choice is made individually by the doctor.
Nitrofurantoin is usually well tolerated with short-term use. The most common side effects are gastrointestinal complaints. A typical, completely harmless accompanying effect is a brownish to yellow-brown discolouration of the urine – it is no cause for concern and disappears again after the course.
| Side effect | Frequency | What to do? |
|---|---|---|
| Brown discolouration of the urine | Common | Harmless, no action needed |
| Nausea, loss of appetite, diarrhoea | Common | Taking with a meal usually eases this |
| Headache, dizziness | Occasional | If persistent, speak to a doctor |
| Lung reaction (cough, shortness of breath, fever) | Rare | Stop immediately and seek medical advice |
| Liver damage, nerve damage | Very rare (esp. long-term) | Seek medical advice |
Nitrofurantoin has fewer interactions than many other antibiotics, because it barely passes into the blood. Even so, there are a few combinations you should know about. Check your preparations in the interaction check.
| Substance / medication | Interaction | Recommendation |
|---|---|---|
| Magnesium-containing antacids | Reduced absorption, weaker effect | Leave a time gap |
| Probenecid, sulfinpyrazone (gout medications) | Less excretion into the urine | Effect in the urine may decrease |
| Quinolone antibiotics (e.g. ciprofloxacin) | Effects can weaken each other | Do not use together |
| Fluconazole (antifungal) | Increased risk of liver and lung reactions | Only after medical assessment |
As targeted as nitrofurantoin is in the bladder, its limits are just as clear. Because the active ingredient is excreted via the kidneys into the urine, with impaired kidney function sufficiently high levels in the urine no longer form – while at the same time the drug level in the blood rises and with it the risk of side effects. That is why nitrofurantoin is not used with markedly reduced kidney performance (GFR below about 45 ml/min).
Likewise, it is not the right agent for a kidney infection (pyelonephritis) or other infections that reach deeper than the bladder: in the kidney tissue and the blood it does not reach effective concentrations. Signs of this are flank pain, high fever and a strong feeling of illness – here an antibiotic that works differently is needed. Nitrofurantoin is also avoided in the last trimester of pregnancy and in newborns.
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