Updated April 2022

What is Allopurinol?

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Allopurinol (brand names Allohexal, Allosig, Progout, Zyloprim) is a medicine used to treat gout, which is a type of arthritis caused by a build up of uric acid crystals in the joints. Cells produce uric acid normally. In gout the body does not flush it out fast enough. 

Allopurinol works by reducing the amount of uric acid made by cells. This helps prevent uric acid crystals building up in the joints and therefore helps prevent joints becoming swollen and painful.

Important things to remember

  • Once you are prescribed allopurinol it is very important that you do not stop taking it unless advised by your doctor or unless side effects develop. If allopurinol treatment is stopped there is a high risk that your gout may worsen.
  • You should continue to take it even if you do not have symptoms.
  • You should also continue to take it during an attack of gout.

What benefit can you expect from your treatment?

Allopurinol is taken on a long-term basis to prevent attacks of gout. The treatment also helps to prevent permanent damage to the joints. It does not treat the pain or inflammation of an ‘attack’ of gout.

Allopurinol does not work straight away. It may take several weeks to reduce the level of uric acid so you may continue to have gout attacks for some time.

Sometimes starting allopurinol or increasing the dose can actually cause an attack of gout. This does not mean the medicine is not working, so keep taking it during such attacks together with any other medicine your doctor may recommend to manage pain.

To reduce the risk of a gout attack, medicines such as colchicine or anti-inflammatory drugs may be recommended before or at the same time allopurinol is started. Your doctor will advise you about how these medicines should be taken.

What happens if you have a gout attack?

Allopurinol is not a pain reliever. You should continue to take allopurinol during an attack, but your doctor will also recommend medicines to treat pain and inflammation. These may include paracetamol, colchicine, anti-inflammatory drugs such as naproxen (Naprosyn), ibuprofen (Brufen/Nurofen), indomethacin (Indocid) or steroids such as prednisolone.

It is a good idea to plan with your doctor what to do if a gout attack occurs and to have symptom controlling medicine ready to use if needed. It is also important that you tell your doctor if your condition persists or worsens.

How is allopurinol taken?

Allopurinol is taken by mouth as a tablet. It is usually taken once a day.

It should be taken after food to reduce stomach upset. It should also be taken with plenty of water.

For greatest benefit, allopurinol should be taken regularly. To help you remember, take it at the same time(s) each day.

If you forget to take a dose, there is no need to double the dose at the next scheduled dose time.

What is the dosage?

Tablets come in 100mg or 300mg strengths. Treatment should start with a small dose, increasing over time to between 100mg and 300mg per day. Higher doses (up to 900mg per day) are needed in some cases. If you have kidney problems the dose may need to be lower. The dose is modified according to the level of uric acid in the blood.

Can other medicines be taken with allopurinol?

Allopurinol may be taken in combination with other arthritis medicines, including:

How long is the treatment continued?

Treatment with allopurinol may be continued indefinitely as long as it is effective and as long as no serious side effects occur.

If you stop allopurinol treatment there is a high risk that your gout may recur. It is very important not to stop your treatment unless advised by your doctor or unless side effects develop.

Are there any side effects?

Most people do not experience side effects from allopurinol. Tell your doctor if you are concerned about any possible side effects.

If you do experience side effects, a reduction in dose may minimise these so that you can continue to take the medicine. Your doctor will advise on any dose changes that are necessary.

Most common possible side effects

  • The most common side effects are nausea or vomiting. These can be reduced if you eat little and often. If you are sick, drink plenty of liquid.

Less common or rare possible side effects

There are some rare but potentially serious side effects with allopurinol.

  • Skin problems: Allopurinol can cause a rash or flaking skin. Very rarely, severe skin rash and mouth ulceration can occur. If any of these occur, contact your doctor straight away.
  • Tiredness: Drowsiness can occur. If it makes you feel sleepy, avoid driving or operating machinery.
  • Liver: Allopurinol can inflame the liver. Blood tests can pick this up if it occurs. The dose of allopurinol may need to be reduced or it may need to be stopped if problems occur. Contact your doctor immediately if you notice yellowing of the skin and/or whites of the eyes.
  • Other: Headache, dizziness, taste disturbances, high blood pressure, feeling generally unwell, and hair loss can occur.

Long term side effects

Allopurinol can be taken for long periods to manage gout. There seems to be no long-term side effects.

Allopurinol does not affect a person’s ability to have children in the long term. See also Precautions.

What precautions are necessary?

Blood tests

  • You may need to have blood tests during the first few months of treatment depending on what other medicines you are taking and depending on your other health concerns. The uric acid level in your blood will be checked to make sure the medicine is working.
  • It is important to see your general practitioner (GP) regularly as they have an important role in monitoring your condition.

Use with other medicines

  • Allopurinol can interact with other medicines. You should tell your doctor (including your general practitioner, rheumatologist and others) about all medicines you are taking or plan to take. This includes over the counter or herbal/naturopathic medicines. You should also mention your treatment when you see other health professionals.
  • Allopurinol increases the blood levels of the immune suppressing medications azathioprine (Imuran) and mercaptopurine (Puri Nethol). Taking allopurinol with either of these medications can be very dangerous. You must tell your doctor if you are taking or are advised to take either of these medications. If either of these medications is taken with allopurinol their dose needs to be very carefully reviewed.
  • Other medicines that may interfere with allopurinol include: warfarin, ampicillin, amoxicillin, thiazide diuretics and sulfinpyrazone.
  • Aspirin can be used safely in the low doses taken for prevention of heart attack and stroke. You should avoid taking aspirin in all other circumstance as at higher doses it can raise the uric acid level.
  • Allopurinol can be taken safely with anti-inflammatory drugs (NSAIDs) provided your kidney function is normal.
  • The pain reliever paracetamol and combined medicines such as Panadeine and Panadeine Forte can be used while taking allopurinol provided you take them as directed.

Use with alcohol

  • Alcohol can trigger an attack of gout. When taking allopurinol, keep your alcohol intake to a safe amount, 1 to 2 standard drinks, several times a week.
  • In addition to alcohol, other things that may trigger an acute gout attack include dehydration, diuretics (fluid tablets) and stopping allopurinol treatment.

Use in pregnancy and when breastfeeding

  • The effects of allopurinol during pregnancy have not been well studied, so it is not clear if it causes birth defects.
  • Gout in women of child-bearing age is uncommon.
  • If you are pregnant or are considering having a child you should discuss this with your doctor before beginning this medication.
  • Allopurinol may be taken when breastfeeding.

How to store allopurinol

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