Allopurinol: preventing gout attacks and kidney stones

The NHS says allopurinol is mainly used to treat gout. It helps reduce the amount of uric acid in the body. Uric acid is a waste product that can cause problems if levels get too high. By lowering it, allopurinol can prevent gout attacks, prevent some types of kidney stones and prevent complications from uric acid build-up during some types of cancer treatment.

It is a preventer. It does not stop an attack that has already begun, which is usually handled separately with other medicines that your doctor will explain.

It comes as tablets or a liquid. You usually take it once a day, though a higher dose may be split up to 3 times a day. How long you need it depends on the reason, and for gout or kidney stones it is often long-term. Swallow tablets whole with a glass of water, though your doctor may ask you to break one in half for a smaller dose. Use the syringe, cup or spoon supplied with liquid. It is best with food, and drinking plenty of fluids is advised.

Do not stop taking it unless your doctor tells you to. If you miss a dose, take it when you remember unless the next dose is close, in which case skip it. Never take two together. An extra dose is unlikely to cause problems, but ask for advice; if you cannot reach a pharmacist or took too much on purpose, call 111.

A counter-intuitive fact the NHS highlights: you may be more likely to get gout attacks when you first start allopurinol, even though it is meant to prevent them. Your doctor will explain this and may prescribe another medicine to cover the early period. The advice is to carry on rather than stop, unless your doctor tells you otherwise.

Blood uric acid levels are usually checked to see whether the dose is working. The linked test guide explains what that result means.

Possible side effects are a rash or other skin reactions, nausea or vomiting, and diarrhoea. A rash is important: stop taking allopurinol and speak to your doctor straight away. It will not usually affect driving, but if you feel drowsy, dizzy or uncoordinated, wait until it passes.

Serious effects are rare. They include anaphylaxis, a severe skin reaction (Stevens-Johnson syndrome, with flu-like symptoms, rash, blisters and sores), meningitis (stiff neck, nausea, severe headache, confusion) and white blood cell problems (easy bruising, great tiredness, sudden sore throat or fever). Call 999 for suspected anaphylaxis, Stevens-Johnson syndrome or meningitis, and 111 for other serious effects.

Most adults can take allopurinol, and it is sometimes prescribed for children with certain cancers. It may not be suitable if you have had a serious reaction to it before, are of Han Chinese, Thai, Korean, African or Indian ethnic origin (more likely to have a severe reaction), or have thyroid, kidney or liver problems.

Tell your doctor if you are pregnant or planning a pregnancy; they may recommend switching to a different medicine, because it is not usually used in pregnancy as it may affect how a baby develops, though a doctor may recommend it if benefits outweigh risks. It can pass into breast milk; it is not known to be harmful, but evidence is limited.

Medicines that may not mix well include aspirin and anticoagulants such as warfarin, theophylline, some blood pressure and heart medicines such as ACE inhibitors and diuretics, some antibiotics such as amoxicillin, and immunosuppressants such as azathioprine. Tell your doctor about all medicines, herbal remedies, vitamins and supplements.

You can eat and drink as normal while taking allopurinol. The NHS page does not give alcohol-specific restrictions, but alcohol is a recognised gout trigger, which your doctor or pharmacist can discuss. If you recently started, a pharmacist can give support through the New Medicine Service.