Nalidixic acid for urine infections

Nalidixic acid is given to treat urine infections.

It is important to complete the full course of treatment unless you are told otherwise. This is to prevent the infection from coming back.

The most common side-effects are feeling sick, diarrhoea, feeling dizzy and headache.

Type of medicineA quinolone antibiotic
Used forTreatment of urine infections
Available asOral liquid medicine

Nalidixic acid is given to treat urine infections. A urine infection is often called a urinary tract infection (UTI) by doctors. Most urine infections are caused by bacteria that come from the bowel. The bacteria thrive in urine and multiply quickly to cause an infection. Nalidixic acid works by stopping the bacteria which are the cause of the infection from multiplying.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking nalidixic acid it is important that your doctor knows:

  • If you are pregnant, trying for a baby, or breast-feeding.
  • If you have ever experienced a problem with your tendons after taking another quinolone antibiotic (these are called ofloxacin, levofloxacin, ciprofloxacin, moxifloxacin, and norfloxacin).
  • If you have been told you have an unusual heartbeat.
  • If you have any problems with the way your liver works, or with the way your kidneys work.
  • If you have epilepsy or any other condition that causes fits.
  • If you have a condition causing tired and weak muscles, called myasthenia gravis.
  • If you have a rare inherited blood disorder called porphyria.
  • If you know you have glucose 6-phosphate dehydrogenase (G6PD) deficiency. This is a genetic disorder which causes problems after eating foods such as fava beans.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start taking the medicine, read the manufacturer's printed information leaflet from the pack. The manufacturer's leaflet will give you more information about nalidixic acid and a full list of the side-effects which you may experience from taking it.
  • Take nalidixic acid exactly as your doctor tells you to. The usual dose for adults is three 5 ml spoonfuls (900 mg) four times daily, for seven days. If you have an ongoing infection, the dose will be reduced to two 5 ml spoonfuls (600 mg) four times daily. The dose will be different to this if the medicine has been prescribed for a child. Shake the bottle well before you measure out a dose.
  • Try to space out the doses over the day - so ideally, take a dose every six hours. You can take nalidixic acid before or after meals.
  • Even if you feel your infection has cleared up, keep taking this antibiotic until the course is finished, unless you are told to stop. This is to prevent the infection from coming back. A course of treatment usually lasts for seven days, although it will be for longer than this if you have a chronic (long-term) infection. If you still feel unwell after finishing the course, go back to see your doctor.
  • If you forget to take a dose, take it as soon as you remember unless your next dose is due. If your next dose is due, then take the dose which is due but leave out the forgotten one. Do not take two doses together to make up for a missed dose.
  • Remember to keep any routine appointments with your doctor. This is so your progress can be monitored. If you are taking nalidixic acid for more than two weeks, your doctor will want you to have some blood tests.
  • Nalidixic acid may cause your skin to become more sensitive to sunlight than normal. Protect your skin by using a sunscreen, particularly if you are exposed to strong sunlight for a prolonged period of time. Do not use sunbeds.
  • If you buy any medicines check with a pharmacist that they are safe to take with this antibiotic. In particular, do not take painkillers called non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, while you are taking nalidixic acid.
  • Some people develop thrush (redness and itching in the mouth or vagina) after taking a course of antibiotics. If you think you have thrush, speak with your doctor or pharmacist for advice.
  • If you are having any urine tests, tell the person doing the testing that you are taking nalidixic acid. This is because the medicine affects some types of urine glucose measurements.
  • This antibiotic may stop the oral typhoid vaccine from working. If you are having any vaccinations, make sure the person treating you knows that you are taking this medicine.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with nalidixic acid. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common nalidixic acid side-effectsWhat can I do if I experience this?
Feeling or being sick, indigestion, stomach acheStick to simple foods - avoid rich or spicy meals. Try taking the medicine after meals if you are not already doing so
DiarrhoeaDrink plenty of water to replace lost fluids. If the diarrhoea is severe or continues to be a problem, speak with your pharmacist or doctor
HeadacheAsk your pharmacist to recommend a suitable painkiller
Feeling dizzyIf this happens, do not drive or use tools or machines until you feel well again

Important: there are also a number of less common but more serious side-effects which have been associated with nalidixic acid. Speak with your doctor as soon as possible if you experience any of the following:

  • An allergic-type reaction, such as swelling around your face or mouth, a skin rash, or any difficulty breathing.
  • Pain or swelling in your joints.

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for advice.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine, ask your pharmacist.

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Helen Allen
Peer Reviewer:
Dr Hannah Gronow
Document ID:
3295 (v25)
Last Checked:
17 April 2014
Next Review:
16 April 2017
The Information Standard - certified member

The information on this page is written and peer reviewed by qualified clinicians.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.