1. About allopurinol
Allopurinol is a medicine used to lower levels of uric acid in your blood. If you produce too much uric acid or your kidneys do not filter enough out, it can build up and cause tiny, sharp crystals to form in and around your joints.
It may also be prescribed if you're having some types of cancer treatment. Some treatments can cause a build-up of uric acid.
Allopurinol comes as 100mg and 300mg tablets and is only available on prescription.
Allopurinol is also known by the brand names Zyloric and Uricto.
2. Key facts
- Allopurinol reduces the amount of uric acid made by your body's cells. This reduces symptoms such as swollen and painful joints (gout).
- It may take several months before you feel the full benefit of allopurinol.
- During the first few months of treatment, as allopurinol starts to work, you may get more gout attacks. However, your doctor will prescribe non-steroidal anti-inflammatory drugs (NSAIDs) or colchicine to help with this.
- When allopurinol is taken regularly, it can lower the number of gout attacks and help prevent damage to the joints.
- Usually you will start allopurinol after an acute attack of gout has completely settled.
3. Who can and cannot take allopurinol
Allopurinol can be taken by adults and sometimes children.
Allopurinol is not suitable for certain people.
Talk to a doctor or pharmacist if you:
- have ever had an allergic reaction to allopurinol or any other medicine
- are of Han Chinese, Thai or Korean origin
- have problems with your liver or kidneys
- currently have an attack of gout
- have thyroid problems
4. How and when to take it
The usual dose of allopurinol is 100mg to 300mg a day. Follow your doctor's advice on how many tablets to take, and how many times a day.
You'll have regular blood tests to monitor your uric acid levels. If your uric acid level does not come down far enough, your doctor may increase your dose (up to 900mg daily in severe cases).
If you have kidney or liver disease, your doctor may prescribe a lower dose and will monitor you more closely.
How to take it
Swallow the allopurinol tablets with water, ideally after food. You'll usually take it once a day, but if you're on a high dose, your doctor may advise you to split the dose and take it twice a day.
If your doctor has recommended you take allopurinol with lots of fluid, try to drink 2 to 3 litres of fluids every day.
You can take allopurinol at any time of the day, however, try to take your doses at the same time of day each day.
Will my dose go up or down?
Your doctor will usually start you on a low dose of allopurinol.
You'll have regular blood tests to monitor your uric acid levels.
Your doctor may increase or decrease your dose depending on the results of your blood tests.
What if I forget to take it?
If you take allopurinol:
once a day – take the missed dose as soon as you remember. If you do not remember until the following day, skip the missed dose.
twice or more a day - if you do not remember until your next dose is due, skip the missed dose and take the dose that is due.
Never take a double dose to make up for a missed dose.
If you often forget to take your medicines, it may help to set an alarm to remind you. You could also ask a pharmacist for advice on ways to help you remember to take your medicines.
What if I take too much?
Urgent advice: Contact 111 for advice now if:
If you need to go to A&E, do not drive yourself. Get someone else to drive you or call for an ambulance.
Take the allopurinol packet or leaflet inside it, plus any remaining medicine, with you.
5. Side effects
Like all medicines, allopurinol can cause side effects, although not everyone gets them.
Common side effects
The most common side effects are feeling or being sick. These can be reduced if you eat little and often and drink lots of fluids such as water or squash. If you are being sick, take small, frequent sips of water to avoid dehydration.
Serious side effects
If you notice a skin rash or redness, tell a doctor straight away, as this can develop into a life-threatening skin condition called Stevens-Johnson syndrome.
Stevens-Johnson syndrome is a rare side effect of allopurinol. It causes flu-like symptoms, followed by a red or purple rash that spreads and forms blisters. The affected skin eventually dies and peels off.
It's more likely to happen in the first 8 weeks of taking allopurinol, or when the dose is increased too quickly. It can also happen if allopurinol is stopped suddenly for a few days and then restarted at the same dose as before. It's better to reduce the dose and then increase it slowly.
It's also best to not start taking allopurinol within 2 weeks of a viral infection, vaccination, or rash caused by something else.
Other serious side effects
It's unusual to have serious side effects after taking allopurinol. Tell a doctor straight away if you:
- get yellow skin or the whites of your eyes go yellow – these can be signs of a liver problem
- get a high temperature, sore throat and swollen glands or feel generally unwell – this could mean there are problems with your white blood cells
- have bruising for no obvious reason or bleeding gums (which takes a long time to stop) when brushing your teeth
- are unusually thirsty, going to the toilet to pee a lot, unusually tired, losing weight without trying, blurred vision – these could be signs of diabetes
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to allopurinol.
Immediate action required: Call 999 or go to A&E now if:
- you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
- you're wheezing
- you get tightness in the chest or throat
- you have trouble breathing or talking
- your mouth, face, lips, tongue or throat start swelling
You could be having a serious allergic reaction and may need immediate treatment in hospital.
These are not all the side effects of allopurinol. For a full list, see the leaflet inside your medicines packet.
You can report any suspected side effect to the UK safety scheme.
6. Pregnancy and breastfeeding
Allopurinol is not usually recommended during pregnancy. There is not enough evidence to say that it's safe.
Talk to a doctor if you're thinking about trying for a baby. There may be other medicines that are safer for you.
Find out more about how allopurinol can affect you and your baby during pregnancy from Best Use of Medicines in Pregnancy (BUMPS).
Allopurinol and breastfeeding
If your doctor or health visitor says your baby is healthy, allopurinol can be taken while you're breastfeeding.
Allopurinol passes into breast milk in small amounts and has been linked with side effects in very few breastfed babies.
If you notice that your baby is not feeding as well as usual, or seems unusually sleepy, or if you have any other concerns about your baby, then talk to your health visitor or doctor.
Non-urgent advice: Tell a pharmacist or doctor if you're:
- trying to get pregnant
7. Cautions with other medicines
Some medicines and allopurinol can interfere with each other and increase the chances of you having side effects.
Tell a doctor or pharmacist if you're taking any of these medicines before you start taking allopurinol:
- aspirin or medicines used to thin your blood (anticoagulants), such as warfarin
- any antibiotics
- medicines used to reduce your immune response (for arthritis or after you've had an organ transplant)
- tablets that make you pee more (diuretics) such as furosemide or ACE inhibitors to treat high blood pressure (hypertension) such as enalapril and ramipril
If you take aluminium hydroxide (found in some antacids such as Maalox and Mucogel), leave a 3 hour gap between the aluminium hydroxide and your allopurinol dose.
Taking allopurinol with painkillers
Your doctor may prescribe a NSAID (such as diclofenac or naproxen or a medicine called colchicine to help prevent or to deal with attacks of gout – especially in the early stages of allopurinol treatment.
Mixing allopurinol with herbal remedies and supplements
There's very little information about taking herbal medicines and supplements with allopurinol.
For safety, tell a doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.
8. Common questions
How does allopurinol work?
Allopurinol works by reducing the amount of uric acid made by body cells.
In gout, this helps prevent uric acid crystals building up in the joints. This helps prevent joints becoming swollen and painful.
In cancer, some cancer treatments kill cancer cells and uric acid is then released from these cells. The build-up of uric acid into crystals can damage the kidneys.
In kidney stones, the waste products in the blood (including uric acid) can make crystals that collect inside the kidneys.
Allopurinol reduces the symptoms caused by the build-up of uric acid in these conditions.
How long does it take to work?
Allopurinol does not work straight away. It may take several weeks to reduce the level of uric acid. You may have more gout attacks for some time after starting allopurinol.
How long will I take it for?
If allopurinol works for you, you may need to take it for the rest of your life to treat gout and kidney stones.
Is it safe to take for a long time?
Allopurinol is considered very safe to take for a long period of time. There are unlikely to be any long-term effects.
What will happen if I stop taking it?
If you stop allopurinol treatment suddenly, there is a high risk that gout may get worse or you will get serious side effects.
Only stop taking allopurinol if a doctor tells you to. A doctor will help you to reduce your dose slowly so you do not get serious side effects.
Are there any other medicines for gout?
There are 2 types of medicine used for gout treatment – some stop the gout attack and some prevent further gout attacks.
Medicines that treat an attack of gout include:
Medicines that treat gout long term in a similar way to allopurinol:
What happens if take allopurinol when I'm having cancer treatment?
Some cancer treatments can cause an increase in uric acid levels in the blood which can then trigger gout attacks. Allopurinol should be started before these particular cancer treatments to prevent the build-up of uric acid.
However, some cancer treatments can cause changes in the blood which can be made worse if you take allopurinol. Your doctor will monitor you carefully and take blood tests if you are at risk.
What effect does allopurinol have on the kidneys and liver?
It's rare for allopurinol to affect the liver or kidneys.
However, if you have serious problems with your kidneys then you may be at greater risk of an allergic reaction to allopurinol. A doctor may prescribe a lower dose of allopurinol.
Allopurinol can also inflame the liver.
Will it affect my contraception?
But if allopurinol makes you vomit, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.
Will it affect my fertility?
There's no firm evidence to suggest that taking allopurinol will reduce fertility in either men or women.
However, talk to a doctor first if you want to try for a baby while taking allopurinol.
Will it affect my sex life?
Allopurinol is not commonly known to affect sex.
However, rarely it can cause breasts to get larger (in both men and women) or erection problems (erectile dysfunction).
Talk to a doctor if you get any of these symptoms.
Can I drive or ride a bike?
Allopurinol can make you feel sleepy.
Do not drive a car, ride a bike, or operate machinery if allopurinol makes you feel sleepy or unable to concentrate or make decisions. This may be more likely when you first start taking allopurinol, but could happen at any time – for example, when starting another medicine.
It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.
GOV.UK has more information on the law on drugs and driving. Talk to a doctor or pharmacist if you're unsure whether it's safe for you to drive while taking allopurinol.
Is there any food and drink I need to avoid?
There are no foods or drink you need to avoid. However, drinking alcohol can trigger an attack of gout.
Can I drink alcohol with it?
Yes, you can drink alcohol while taking allopurinol. But drinking alcohol increases the level of uric acid in your blood and can trigger an attack of gout.
If you feel OK, you can drink alcohol in moderation. Following the national guidelines on alcohol for men and women of drinking no more than 14 units of alcohol a week. 14 units is equivalent to 6 pints of average-strength beer or 10 small glasses of low-strength wine.
Can lifestyle changes help gout?
Making lifestyle changes might mean you can stop or reduce further attacks of gout.
- get to a healthy weight, but avoid crash diets – you could try the NHS weight-loss plan
- eat a healthy, balanced diet that includes plenty of vegetables and some low-fat dairy foods
- have at least 2 alcohol-free days a week
- drink plenty of fluids to avoid getting dehydrated
- exercise regularly – but avoid intense exercise or putting lots of pressure on joints
- stop smoking
- do not eat a lot of red meat, kidneys, liver, or seafood
- do not have lots of sugary drinks and snacks
- do not have lots of fatty foods
- do not drink more than 14 units of alcohol a week