Indications
Nitrofurantoin is an antibiotic used to treat uncomplicated lower urinary tract infections (cystitis, or bladder infection) caused by bacteria such as E. coli, and to help prevent repeated bladder infections in people who get them often. It is not suitable for kidney infections (pyelonephritis) or infections that have spread into the blood, because it does not reach high levels outside the bladder. This product contains the microcrystalline form, often in a sustained-release capsule.
How It Works
Nitrofurantoin is concentrated in the urine. There, bacterial enzymes turn it into reactive substances that damage bacterial DNA, proteins and cell walls, killing the bacteria. Because it attacks several targets at once, resistance develops slowly.
Dosage and Administration
For treatment in adults, a common dose of the sustained-release (modified-release) form is 100 mg twice a day for 3 to 7 days, or as prescribed; other forms have different schedules. For prevention, a lower dose is usually taken once at bedtime, as prescribed. Take it with food or milk, which improves absorption and reduces stomach upset. Swallow capsules whole. Complete the course, and drink plenty of fluids.
Interactions
- Antacids containing Magnesium Trisilicate: reduce absorption; avoid taking together.
- Probenecid and Sulfinpyrazone: can reduce the amount reaching the urine and increase side effects.
- Medicines that make the urine alkaline (such as Potassium Citrate): reduce its effect.
- Live oral typhoid vaccine: may be less effective.
- It can affect some urine glucose tests.
Contraindications
- Reduced kidney function (generally an eGFR below 45 ml/min, or as judged by the doctor), because it does not work well and side effects increase.
- G6PD deficiency (risk of haemolysis).
- Pregnancy at term (38 to 42 weeks), during labour and delivery, and in babies under 3 months old.
- Previous liver problems or lung reactions caused by Nitrofurantoin.
- Allergy to Nitrofurantoin or other nitrofurans.
- Acute porphyria.
Side Effects
Common effects include nausea, loss of appetite, headache, dizziness and drowsiness. Urine may turn dark yellow or brown, which is harmless. Less often, it can cause rash, diarrhoea or hair thinning. Rarely, especially with long-term use, it can cause lung inflammation, liver damage or nerve damage.
Get urgent medical help if you develop sudden fever, chills, cough, chest pain or breathlessness; yellow skin or eyes, dark urine with pale stools or severe tiredness; numbness, tingling or weakness in the hands or feet; severe or bloody diarrhoea; or signs of a severe allergic reaction.
Pregnancy and Lactation
Nitrofurantoin can be used in pregnancy when a doctor prescribes it, but it must be avoided near term, during labour and delivery because it can cause haemolysis in the newborn. Small amounts pass into breast milk; avoid breastfeeding an infant under 1 month old or one with G6PD deficiency, and ask your doctor.
Precautions and Warnings
People on long-term preventive treatment need regular checks of lung and liver function, and should report any breathing problems, cough or tingling. Use with care in older adults, and in people with diabetes, anaemia, vitamin B deficiency or electrolyte imbalance, which increase the risk of nerve damage. See a doctor if symptoms do not improve in 2 to 3 days.
Overdose
Overdose may cause vomiting and stomach upset. Contact a doctor or poison centre; drinking extra fluids helps remove the medicine.
Therapeutic Class
Urinary antibacterial (nitrofuran).
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.