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  • Used to prevent gout attacks and kidney stones
  • Reduce uric acid levels in the blood
  • Take tablet with food

About Allopurinol

Allopurinol belongs to a group of medicines called enzyme inhibitors. The active ingredient works by slowing down the speed of certain chemical reactions in your body to lower the level of uric acid in the blood and urine. This medicine is used to treat various conditions, including:

  • Gout. In gout the uric acid builds up in your joints and tendons as crystals. These crystals cause an inflammatory reaction.
  • Kidney stones. Kidney stones form when urine becomes supersaturated with certain substances. If kidney stones travel down the ureter they may get stuck, causing extreme pain. Most kidney stones pass out of the body in the urine after several days.

Allopurinol lowers levels of uric acid in the body. This lowers the risk of kidney stones and reduces symptoms of gout.

How to use Allopurinol

Allopurinol tablets should be taken with plenty of water, preferably with food to reduce the risk of possible side effects.


Dosage varies per person and is determined by a doctor depending on the symptoms. The general dosage guidelines are as follows:

  • Adults: the recommended starting dose is 100 to 300 mg per day, taken as a single dose. The dose can be increased to 900 mg if necessary, depending on the severity of your condition.

If you are taking a daily dose of more than 300 mg, your doctor may advise to split the dose in smaller portions and spread them out as evenly as possible to reduce the risk of side effects in the stomach and digestive system.

The doctor may prescribe a different dose for the elderly, children aged 15 to 18, and patients with a decreased kidney or liver function. For more information on dosage, see the package leaflet.


Allopurinol may cause drowsiness or affect your coordination. If you experience these symptoms you should avoid driving or operating machinery.

This medicine does not interact with alcohol.

If you use too much/forget to use/stop using Allopurinol

If you swallow too many tablets or someone else accidentally takes your medicine, contact your doctor or nearest hospital emergency department immediately. Take the box and any tablets that are left over with you, if you can. Signs of an overdose may include nausea, vomiting, diarrhoea and dizziness.

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose,

skip the forgotten dose and continue as usual. Do not take a double dose to make up for a forgotten one.

Do not stop using Allopurinol without talking to your doctor.

When not to use Allopurinol

Allopurinol is not suitable for everyone. Do not use this medicine if:

  • You are allergic to any of the ingredients in this medicine (see section ‘What Allopurinol contains').

When should this medicine be used with caution?

Talk to your doctor or pharmacist before taking this medicine if:

  • You have, or have had, problems with your liver or kidneys.
  • You are taking medication to treat certain heart conditions or high blood pressure (e.g., diuretics or ACE inhibitors).
  • You are currently having an attack of gout.
  • You are of Han Chinese, Thai or Korean origin.
  • You have thyroid problems.

Take special care with this medicine:

  • If you have kidney stones. The kidney stones will become smaller and may enter your urinary tract.
  • Serious skin rashes have been reported in patients taking allopurinol, including:
    • Hypersensitivity syndrome.
    • Severe allergic reaction with high fever.
    • Widespread blistering of the skin.
    • Joint pain and/or red and swollen eyes (Stevens-Johnson syndrome) and severe and sudden allergic reaction, accompanied by fever and blistering and peeling of the skin (see the package leaflet for more information). If you develop a rash or these skin symptoms, stop using Allopurinol and contact your doctor immediately.
  • If you have cancer or a metabolic disorder called LeschNyhan syndrome, the amount of uric acid may increase in your urine. To prevent this, you need to assure you drink sufficiently to dilute your urine.

Pregnancy and breastfeeding

If you are pregnant or breastfeeding, think you may be pregnant or are planning to get pregnant, ask your doctor or pharmacist for advice before using this medicine.

Allopurinol is excreted in the human breast milk. Allopurinol during breastfeeding is not recommended.

Other medicines and Allopurinol

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. This is because Allopurinol can affect the way some medicines work. Also some other

medicines can affect the way Allopurinol works. For example:

  • Medicines used to reduce your immune response (immunosuppressants) e.g., 6‑mercaptopurine, azathiopine, ciclosporin.
  • Adenine arabinoside (vidarabine), used to treat herpes or chickenpox.
  • Other medicines to treat gout, such as probenecid.
  • Acetylsalicylic acid such as aspirin (or related medicines called salicylates).
  • Chlorpropamide, used to treat diabetes.
  • Medicines which thin the blood (anticoagulants), such as warfarin.
  • Medicines used for fits (epilepsy), phenytoin.
  • Theophylline, used for breathing problems.
  • Antibiotics used to treat bacterial infections (amoxicillin or ampicillin).
  • Medicines used to treat cancer.
  • Didanosine, used to treat HIV infection.
  • Medicines for heart problems or high blood pressure such as ACE inhibitors or water tablets (diuretics).
  • Aluminium hydroxide (used to neutralise the acid in the stomach) as it may weaken the effect of allopurinol. There should be an interval of at least three hours between taking both medicines.
  • Some chemotherapy medicines (e.g., cyclophosphamide, doxorubicin, bleomycin, procarbazine, alkyl halogenides) as blood disorders occur more frequently with concomitant use of Allopurinol and these medicines. Blood count monitoring should therefore be performed at regular intervals.

Side effects

Like all medicines, this medicine can cause side effects, although some people may not experience any. Side effects that are known to be associated with Allopurinol include:

Allergic reaction

Uncommon (may affect up to 1 in 100 people):

  • If you have a hypersensitivity (allergic) reaction, stop taking Allopurinol and see a doctor straight way. The signs may include: flaking skin, boils or sore lips and mouth, or very rarely sudden wheeziness, fluttering or tightness in the chest and collapse.

See the package leaflet for more hypersensitivity reactions.

Other side effects

Common (may affect up to 1 in 10 people):

  • Skin rash.
  • Increased level of thyroid stimulating hormone in the blood.

Uncommon (may affect up to 1 in 100 people):

  • Feeling sick (nausea) or being sick (vomiting).
  • Changes in liver function tests.
  • Diarrhoea.

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

  • Liver problems (e.g., hepatitis).

For a complete list of side effects, see the package leaflet. If you get any side effects, talk to your doctor. This includes any possible side effects not listed in this package leaflet.

What Allopurinol contains

The active substance is allopurinol. Each 100-mg tablet of Allopurinol contains 100 mg of allopurinol. Each 300-mg tablet of Allopurinol contains 300 mg of allopurinol.

Package leaflet

Read the package leaflet before use. The official package leaflet of Allopurinol is available for download here.

Patient Leaflet(s)

Reviewed by:

Dr Wouter Mol, General practitioner Registrationnumber: BIG: 9057675501 Last checked: 12-09-2023 | Still valid

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