Nalidixin

Indications

• Urinary tract infections caused by bacteria that are sensitive to it, mainly simple bladder infections.
• Some bowel infections, such as bacillary dysentery (shigellosis), where local guidance and testing show it still works.

Many bacteria are now resistant to Nalidixic Acid, so the doctor may choose a different antibiotic.

How It Works

Nalidixic Acid is an older quinolone antibacterial. It blocks an enzyme (DNA gyrase) that bacteria need to copy their genetic material, so the bacteria cannot multiply. It reaches high levels in the urine, which is why it is mostly used for urine infections.

Dosage and Administration

Adults, acute urinary infection: usually 1 g four times a day (about every 6 hours) for 7 days, or as prescribed. Long-term (chronic) infection: the doctor may use a lower dose, such as 500 mg four times a day.

Children: the dose depends on body weight and is given only as prescribed. It is not used in babies under 3 months.

Take with a glass of water. Shake the suspension well before use. Finish the full course even if you feel better.

Interactions

Antacids and products containing iron, zinc, calcium or magnesium can reduce absorption; take them at least 2 hours apart. Nalidixic Acid can increase the effect of Warfarin. It should not be taken with Nitrofurantoin, which can block its action. Probenecid can change its levels. Tell your doctor about all medicines, vitamins and herbal products you take.

Contraindications

• Allergy to Nalidixic Acid or other quinolone antibiotics
• History of seizures (epilepsy)
• Porphyria
• Babies under 3 months

Side Effects

Common: nausea, vomiting, stomach pain, diarrhoea, headache, dizziness, drowsiness, rash and itching.

Others: skin reactions in sunlight, blurred vision or changes in colour vision, and, in people with G6PD deficiency, breakdown of red blood cells.

Get medical help at once for a seizure; swelling of the face or throat or difficulty breathing; severe or bloody diarrhoea; tendon pain or swelling; dark urine with pale skin; or, in a child, severe headache, vomiting or a bulging soft spot on the head.

Pregnancy and Lactation

Nalidixic Acid is usually avoided in pregnancy, especially in the first 3 months and near delivery; the doctor will choose a safer antibiotic. Avoid while breastfeeding, particularly if the baby has G6PD deficiency or is newborn.

Precautions and Warnings

• Avoid strong sunlight and sunlamps during treatment.
• Take extra care with liver or kidney disease, G6PD deficiency, or myasthenia gravis.
• Drowsiness or visual changes can affect driving or using machines.
• Older people may be more prone to tendon problems.

Overdose

Overdose can cause vomiting, confusion, visual problems and seizures. Contact a doctor or go to hospital straight away; treatment is supportive.

Therapeutic Class

Quinolone antibacterial (urinary antibacterial).

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.