What is allopurinol and how is it used?

Allopurinol (al-oh-pure-ri-nol) is mainly used for the long-term treatment and prevention of gout. Taken regularly, it can stop attacks of gout and help prevent damage to your joints.

It can also be used for treating kidney stones.

The body naturally produces a substance called urate. This normally dissolves in your blood until it’s passed out of the body in your urine. When too much urate is produced, or if your body can’t get rid of it properly, crystals can form in and around your joints. This causes pain and inflammation.

Allopurinol blocks an enzyme that is involved in producing urate. This helps the crystals to dissolve and stops attacks of gout.

Allopurinol can lower the urate levels in your blood over the space of a few weeks. This will stop new crystals forming.

It can take longer to dissolve crystals that are already there, and you may have more attacks of gout during this time. This is more likely to happen if your urate levels are very high or you’ve had gout for a long time. If this happens to you, it doesn’t mean that your allopurinol isn’t working.

Attacks of gout usually stop within a year, as long as your urate level has gone down enough.

Your doctor will usually be cautious about prescribing allopurinol if you have kidney, thyroid or liver problems.

You will usually be offered allopurinol for gout if blood tests show that your urate level is high and one or more of the following applies:

  • You keep having attacks of gout.
  • Your joints or kidneys have been damaged by attacks of gout.
  • Your skin has been affected by deposits of urate crystals.

When and how do I take allopurinol?

Your doctor may advise you not to start taking allopurinol until after an acute (bad) attack of gout has passed. If this isn’t possible, it may be started while the gout isn’t as bad.

Allopurinol isn’t a treatment for acute attacks of gout.

Allopurinol is taken as a tablet once a day. It’s usually better to take it just after eating. The tablet should be swallowed with water. It is important to drink plenty of water during the day.

Your doctor will advise you about the correct dose. Your dose will vary, depending on the urate level shown in your blood tests. You may need a lower dose if you have kidney or liver disease. 

It can take two to three months for your urate levels to reduce to a suitable level. You will then have checks every few months to make sure the urate isn’t increasing.

You may be able to make lifestyle changes that can reduce the risk of you getting gout, or of gout returning. These include:

  • not eating too much protein
  • avoiding foods that are high in purines, such as seafood, kidneys and liver
  • avoiding foods that are high in yeast extracts, such as Marmite
  • not having sugary drinks
  • reducing the amount of alcohol you consume
  • trying to lose weight, if you are overweight
  • drinking enough water. Try to drink up to two litres a day.

It’s likely that you will need to take allopurinol for the rest of your life. You should keep taking allopurinol even:

  • if it doesn’t seem to be working at first
  • if you have more attacks of gout when you first start allopurinol
  • when you stop having attacks of gout – if you do this, your urate levels may start to build up again and your symptoms may return.

However, if you get side effects, speak to your GP or rheumatology team.

Possible risks and side effects

Side effects of taking allopurinol can include:

  • skin rashes
  • headaches
  • feeling drowsy or dizzy
  • feeling or being sick
  • changes to your sense of taste.

If you develop a rash, you should stop taking your allopurinol and contact your doctor straight away. If you become dizzy or drowsy while taking allopurinol, don’t drive or operate machinery, and see your doctor as soon as possible. You should also speak to your doctor if you develop any other new symptoms that concern you.

Most people who take allopurinol don’t get any side effects. But if you do have side effects, it may be possible to restart allopurinol using a special ‘desensitisation’ course. This involves beginning allopurinol at a very low dose and increasing the dose gradually.

Sometimes starting allopurinol can actually trigger an attack of gout, as the crystals begin to dissolve. You will probably be given an extra medicine for the first few months of taking allopurinol to reduce the risk of these attacks happening.

Acute attacks of gout are usually treated with a high dose of a non-steroidal anti-inflammatory drug (NSAID), such as:

  • diclofenac sodium (die-clo-fe-nac sow-dee-um)
  • diclofenac potassium (die-clo-fe-nac po-tass-ee-um)
  • etoricoxib (ee-torry-cox-ib)
  • indomethacin (in-doe-meth-a-sin)
  • ketoprofen (key-toe-pro-fen)
  • naproxen (na-procks-en)
  • sulindac (suh-lin-dak).

These drugs all have brand names, so the type you’re given may be called something different.

If you cannot take NSAIDs, colchicine (coal-chi-seen) or steroids may be given.

If you do have an acute attack of gout while on allopurinol, don’t stop taking it.

If you’re unable to continue taking allopurinol because of your side effects, you may be able to take febuxostat instead, which works in a similar way to allopurinol.

If you can’t take febuxostat, your doctor may suggest benzbromarone (bens-bro-ma-rone) or sulfinpyrazone (sul-fin-pira-zone).

However, allopurinol should not be used to treat an acute attack of gout. This is because they may make the attack last longer.

Tips to reduce your risk of infection

  • Try to avoid close contact with people you know have an infection.
  • Wash your hands regularly and carry around a small bottle of antibacterial hand gel.
  • Keep your mouth clean by brushing your teeth regularly.
  • Stop smoking if you’re a smoker.
  • Make sure your food is stored and prepared properly.
  • Try to keep your house clean and hygienic, especially the kitchen, bathrooms and toilets.

Can I take other medicines alongside allopurinol?

Some drugs interact with allopurinol, so you should discuss any new medication with your doctor before starting it. You should also tell anyone else treating you that you’re taking allopurinol.

You’ll probably need to take an NSAID, colchicine or steroids to help prevent or treat with attacks of gout. This is most likely to happen when you first start taking allopurinol.

It is fine to take paracetamol or an NSAID with allopurinol. However, you should not take more than one anti-inflammatory at a time, unless a doctor tells you to. This is because it increases the risk of bleeding from the stomach. For this reason, you shouldn’t take aspirin if you have gout.

Allopurinol interacts with the drugs azathioprine and mercaptopurine.

Azathioprine can used for treating conditions such as:

  • rheumatoid arthritis (roo-ma-toy-d arth-ri-tus)
  • Crohn's disease (kro-wnz diz-eez)
  • ulcerative colitis (ul-ser-ay-tive col-eye-tis)
  • lupus (loo-pus)
  • dermatomyositis (der-mer-toe-my-oh-sigh-tus)
  • hepatitis (hep-er-tie-tus)
  • vasculitis (vask-you-lie-tis).

Mercaptopurine (mer-cap-toe-pure-reen) is used for treating leukaemia.

These drugs should not generally be taken with allopurinol.

Allopurinol may increase the risk of developing a rash if you take them with the antibiotics ampicillin (amp-ear-cil-in) or amoxicillin (a-mox-ear-cil-in).

Allopurinol may increase the effect of warfarin and other drugs that thin the blood. These are known as anticoagulants. As a result, you may need to have your blood clotting tested more frequently.

Vaccinations

You can have vaccinations while on allopurinol.

Alcohol

There’s no known interaction between alcohol and allopurinol. However, alcohol increases the amount of urate in the blood.

Try to keep within government guidelines, which say that both men and women should drink no more than 14 units of alcohol a week. You should spread these through the week, rather than having them all in one go.

For more information about units of alcohol, visit www.drinkaware.co.uk.

Fertility, pregnancy and breastfeeding

Allopurinol is unlikely to affect fertility.

However, we don’t know what effect allopurinol has on an unborn baby. As a result, you shouldn’t take it if you’re pregnant. If you’re planning a family, or become pregnant while taking allopurinol, talk to your doctor.

Some allopurinol will pass into breast milk, but the risk to the baby is unknown. Therefore, you shouldn’t breastfeed if you’re taking allopurinol.