Nitrofurantoin

What is nitrofurantoin?

Nitrofurantoin is an antibiotic that is used to treat cystitis, an inflammation of the bladder. Cystitis is commonly caused by an infection and is therefore referred to as a ‘urinary tract infection’ (UTI). UTIs occur when bacteria enters through the urethra into the bladder and begin to multiply. Women are more prone to UTIs as the female urethra is shorter, making it easier for bacteria to travel from the skin into the urethra and bladder.

How does nitrofurantoin work?

Nitrofurantoin works by stopping the bacteria from repairing themselves or multiplying, which eventually kills off the bacteria and clears the infection.

How long does it take for nitrofurantoin to work?

Nitrofurantoin will start to work within a few days. The length of treatment is usually 3 days for an uncomplicated mild infection in women. It's important to keep taking the medicine for the length of time prescribed by your doctor to ensure that the infection has been adequately treated. 

Active ingredients

Each capsule contains 50mg of nitrofurantoin as the active ingredient.

Inactive ingredients

The inactive ingredients in the medication are lactose, maize starch, pregelatinised maize starch, sodium starch glycollate and magnesium stearate.

Please note: different generic brands of nitrofurantoin may contain different inactive ingredients.

Which ingredients can cause an allergic reaction?

Signs of an allergic reaction include itchiness, difficulty breathing, rash, feeling faint, and facial/throat swelling. While a severe allergic reaction to this medication is rare, if you notice these symptoms after taking this antibiotic, you should keep medical attention right away as it can be fatal without treatment.

How to take it?

Always use nitrofurantoin as instructed by your doctor. The dose and frequency you take will depend on the type of infection you have. The standard dose to treat a UTI is 200mg a day which is split into either 100mg twice per day, or 50mg four times per day. Your treatment will last for 3–7 days and it is important that you finish your course of antibiotics to ensure that the infection is treated effectively and will not resurface or develop resistance.

When should you start nitrofurantoin?

You should start taking nitrofurantoin as soon as possible, as prescribed. If you are taking it twice a day, then leave 12 hours between your doses. For example, if you take your morning tablet at 9am then wait until 9pm to take your evening one. If you are asked to take a tablet four times per day, try to space them out as equally as possible, for example, first thing in the morning, midday, afternoon and before bed. 

Do I need to finish a course of nitrofurantoin, even when my symptoms have resolved?

It's important to keep taking nitrofurantoin even if your symptoms appear to have disappeared and you are feeling better. If you stop taking it before you are supposed to then this leaves you at risk of the infection returning.

What if I take too many nitrofurantoin tablets?

If you have taken too many nitrofurantoin tablets, speak to a doctor or pharmacist for advice. Even if you don't experience any side effects if you are worried then reach out for advice.

Nitrofurantoin side effects

Like all medications, nitrofurantoin can cause side effects. 

Tell your doctor if you experience any of the following side effects: 

• Tingling, weakness or numbness in your muscles or joints 
• Jaundice (yellowing of the skin)
• Fever, chills, chest pain, coughing or shortness of the breath
• Feeling unwell alongside unexplained bruising or bleeding and feverish symptoms
• A severe headache 
• Swelling in the mouth, lips, tongue or throat; difficulty breathing; a rash or tightness in the chest. This is a sign of an allergic reaction. 

Common side effects (may affect up to 1 in 100 people) include: 

• Vomiting (being sick)
• Stomach pain
• Diarrhoea
• Headache
• Nitrofurantoin commonly causes your urine to turn dark yellow or brownish. This is a normal side effect and not something to worry about. Your urine should return to normal when you finish the course and stop taking nitrofurantoin. 

Rare side effects (may affect up to 1 in 1,000 people)

• Deficiency of red blood cells (aplastic anemia)
• Loss of consciousness (collapse)
• Bluish discolouration of the skin (cyanosis)
• Psychological changes such as depression, a feeling of intense excitement and happiness (euphoria), confusion and psychotic reactions
• Weakness, numbness and pain in the hands and feet (peripheral neuropathy)
• Blurred vision
• Vertigo, unusual eye movements (nystagmus), headache, dizziness or drowsiness
• Long-term changes to the lungs (chronic pulmonary reactions)
• Jaundice (inflammation of the liver causing yellowing of the skin or whites of the eyes), inflammation of the liver (hepatitis) which may be fatal, liver failure
• Flaking skin or a rash

Contraindications

Before taking Nitrofurantoin inform your doctor if you have: 

• Ever had an allergic reaction to the medicine or any others 
• Porphyria or glucose-6-phosphate dehydrogenase
• Diabetes
• Kidney disease 
• Anaemia 
• Vitamin B deficiency 
• A condition which causes significant weakness 
• Lung disease

Drug interactions

Always inform your doctor of any other medications you are taking. In particular, if you are taking: 

• Antacids 
• Medications to treat gout
• Over the counter remedies for cystitis 
• Quinolones
• Medicines that slow the passage of food through the stomach (e.g. atropine, hyoscine)
• Medicines for increased pressure in the eye (glaucoma), such as carbonic anhydrase inhibitors (e.g. acetazolamide).
• Medicines that make the urine less acidic (e.g. potassium citrate mixture). 

How to cope with nitrofurantoin side effects?

Drink plenty of water and make sure you stay hydrated if you experience headaches or sickness. You can take over the counter painkillers like paracetamol and ibuprofen to clear up a headache and make sure you get enough rest if you get sick or have diarrhoea. If you get dizzy spells then sit or lie down until it passes and do not overexert yourself while you are feeling lightheaded or unwell. Taking nitrofurantoin with food can help to ease nausea, as can eating smaller meals, avoiding anything too rich or spicy.

Will Nitrofurantoin interfere with my fertility?

Nitrofurantoin has not been shown to affect fertility in either women or men. If you are planning to get pregnant, then discuss this with your doctor before taking nitrofurantoin to ensure the treatment is suitable for you.

Nitrofurantoin and alcohol

You can drink alcohol with nitrofurantoin without it having an adverse effect. However alcohol can make symptoms of a urine infection worse, so it’s best to avoid drinking until you’re feeling back to normal.

Does nitrofurantoin cause/aggravate thrush? - Why?

Taking nitrofurantoin for a prolonged period of time can cause thrush. This is because the antibiotic destroys some of the bacteria present in the body which protects you from developing thrush. This generally doesn’t happen when nitrofurantoin is only taken for a short period of time (<7 days). If you experience symptoms of thrush then seek treatment from your doctor or pharmacist, letting them know that you are taking nitrofurantoin.

Nitrofurantoin and pregnancy

Nitrofurantoin is safe to use during pregnancy.

How to avoid UTIs?

There are some things you can do to help prevent a UTI. These include: staying hydrated to keep your urine dilute, which will help to flush out bacteria; wiping from front to back after using the toilet and urinating after sexual intercourse to empty the bladder. Contraceptive methods that use spermicide can also encourage bacteria growth, as can using perfumed feminine washes, powders or sprays around the genitals.

Alternatives to nitrofurantoin

Other medications which may be given to treat a UTI include trimethoprim, cefalexin, ciprofloxacin and amoxicillin.

Macrobid vs nitrofurantoin

Macrobid is a brand name of nitrofurantoin which is an extended-release version, meaning it only needs to be taken twice a day. Both medicines work in the same way to treat infections of the bladder.

Cranberry juice and nitrofurantoin

There is no reliable evidence to suggest that drinking cranberry juice can have an effect on nitrofurantoin or help to ease the symptoms of a UTI, but it is unlikely to cause any harm and can help you keep hydrated. 

Does nitrofurantoin work for UTIs in men?

Nitrofurantoin can be prescribed to treat UTIs in men, however, typically a longer course is required for men than women. If you’re male and have symptoms of a UTI, speak to your doctor to discuss the best treatment option.

Is nitrofurantoin an antibiotic?

Nitrofurantoin is an antibiotic that becomes concentrated in the urine where it works to kill off the bacteria causing infection.

Can nitrofurantoin help an STI?

Nitrofurantoin will not combat the bacterial infections causing STIs such as chlamydia and gonorrhoea. If you are worried you have an STI, it’s important to get tested.

Does nitrofurantoin treat kidney infections?

Nitrofurantoin may be used to treat a kidney infection but it is not always effective. Your doctor will assess your symptoms and the severity of your infection before prescribing you an appropriate medication. If you think you have a kidney infection it’s important to see your doctor. 

Does nitrofurantoin affect contraception?

Nitrofurantoin does not interfere with contraception. However, you might want to avoid sex until your symptoms have cleared up, to maximise the effectiveness of treatment.