Nitrofurantoin
Indications
Nitrofurantoin is an antibiotic used to treat uncomplicated infections of the bladder (lower urinary tract infection, cystitis). It is also used in low doses to prevent repeated urinary infections. It is not suitable for kidney infections or infections that have spread into the blood, because it does not reach useful levels outside the urinary tract.
How It Works
Nitrofurantoin is concentrated in the urine. Bacteria convert it into reactive substances that damage their DNA, proteins and cell walls, which kills them.
Dosage and Administration
- Adults, bladder infection: usually 50 mg four times a day (standard capsules or tablets), or 100 mg twice a day (modified-release capsules), for 3 days in women, or 7 days in men or as the doctor advises.
- Preventing repeated infections: usually 50 to 100 mg once a day at bedtime, as prescribed.
- Take with food or milk to reduce nausea and improve absorption. Finish the full course.
- Children: as prescribed.
Interactions
Antacids containing magnesium trisilicate reduce absorption; take them at a different time. Probenecid and Sulfinpyrazone can lower urine levels of Nitrofurantoin and raise blood levels. It may reduce the effect of quinolone antibiotics such as Nalidixic Acid. It can cause false positive results in some urine sugar tests.
Contraindications
- Significantly reduced kidney function, where the medicine does not work well and side effects are more likely.
- G6PD deficiency (risk of breakdown of red blood cells).
- Babies under 3 months of age.
- Late pregnancy (from 38 weeks), during labour and delivery.
- Acute porphyria, or allergy to Nitrofurantoin or similar medicines.
Side Effects
Common: nausea, loss of appetite, headache and dizziness. Urine may turn dark yellow or brown; this is harmless.
Get urgent medical help for: sudden breathlessness, cough, fever, chills or chest pain (a lung reaction, which can happen within days or after long use); numbness, tingling or weakness in the hands or feet; yellowing of the skin or eyes; a severe skin rash with blistering or peeling; swelling of the face or throat; or severe or bloody diarrhoea.
Pregnancy and Lactation
It can be used in early and mid pregnancy if the doctor advises, but must be avoided near the end of pregnancy (from 38 weeks) and during labour because it can harm the newborn's red blood cells. It passes into breast milk in small amounts; avoid if the baby is under 1 month old or has G6PD deficiency, and ask the doctor otherwise.
Precautions and Warnings
- Long-term use needs regular checks of the lungs, liver and nerves; report any new cough or breathlessness at once.
- Older people, and people with diabetes, anaemia, vitamin B deficiency or kidney problems, are at higher risk of nerve damage.
- See the doctor if symptoms do not improve within 2 to 3 days, or if you develop fever, back or side pain, as this may be a kidney infection.
Overdose
Too much may cause vomiting. Seek medical advice; drinking plenty of fluids helps the body remove it.
Therapeutic Class
Urinary antibacterial (nitrofuran antibiotic).
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.
All brands of Nitrofurantoin