Easy-to-read medicine information about allopurinol – what it is, how to take allopurinol safely and possible side effects.
Type of medicine
Medicine to prevent gout
Belongs to a group of medicines known as urate lowering therapy
What is allopurinol?
Allopurinol is used as a long-term treatment to prevent gout attacks or flares. It can also be used to prevent some types of kidney stones and may be used in people receiving cancer chemotherapy, to prevent high uric acid (measured as urate in the blood or 'serum urate') levels. In New Zealand allopurinol is available as 100 milligram and 300 milligram tablets.
Allopurinol helps reduce urate levels in your blood (serum urate) and reduces gout attacks.
Uric acid is a normal product of your metabolism and in the blood, uric acid becomes urate. When urate levels are high, crystals can form around joints causing inflammation, pain and damage. This is known asgout.
To reduce gout attacks, it is important to keep your serum urate level below 0.36 mmol/L. When the serum urate is below 0.36mmol/L no new crystals form and crystals that are in your joints or skin can dissolve. Read more about gout.
The dose of allopurinol will be different for different people.
Your doctor will usually start you on a low dose (50 or 100 milligrams each day) and increase it very slowly over a few months. Your doctor will test your serum urate with a blood test and increase the allopurinol dose as much as needed until a serum urate level of less than 0.36 mmol/L is reached.
The usual dose of allopurinol is 300 milligrams or more daily. Some people may need between 600 and 900 milligrams daily.
Always take your allopurinol exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions. Know what dose you should be taking - if you are unsure, talk to your pharmacist.
My dose is:
How to take allopurinol
Timing: Take allopurinol once a day with a full glass of water. If you think allopurinol is causing stomach upset, try taking it with food.
Drink plenty of water. It is important to drink plenty of water while you are taking allopurinol because kidney stones can develop if you do not drink enough fluid.
Limit or avoid alcohol while you are taking allopurinol. Alcohol can trigger an attack of gout.
Missed dose: If you forget to take your dose of allopurinol, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
Keep taking allopurinol every day, even during a gout attack. Allopurinol takes 2 to 3 months to become fully effective. Do not stop taking allopurinol suddenly; speak to your doctor or nurse before stopping. Stopping allopurinol quickly can make your gout worse. Read more frequently asked questions about allopurinol.
Precautions when taking allopurinol
Before starting allopurinol
Are you pregnant or breastfeeding?
Do you have problems with your liver or kidneys?
Are you taking any other medicines? This includes any medicines you buy without a prescription, such as herbal and complementary medicines.
If so, it’s important that you tell your doctor or pharmacist before you start allopurinol or any new medicines. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.
While taking allopurinol
Increased gout attacks: when you start taking allopurinol, gout attacks can still happen in the first few weeks or months, as you are increasing your dose. When you start allopurinol, your doctor will also prescribe a low-dose non-steroidal anti-inflammatory (NSAID) or colchicine to reduce the chances of these attacks. Keep taking allopurinol every day, even during a gout attack.
Blood tests: when you first start taking allopurinol, you will need to have blood tests to monitor your serum urate levels every 4 weeks until the target level has been reached. Then you will need blood tests 3-6 monthly to check serum urate and your kidney function.
Like all medicines, allopurinol can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.
What should I do?*
Skin rash or itching (about 2 in every 100 people who take allopurinol will have a skin rash)
Stop taking allopurinol
Contact your doctor immediately – even if the rash is mild. This can develop into a severe allergic reaction.
Stomach upset, nausea (feeling sick), or vomiting
This is quite common when you first start taking allopurinol.
Allopurinol may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting allopurinol or before starting any new medicines. Do not take azathioprine with allopurinol except under specialist supervision.
The following links have more information on allopurinol.
Credits: Sandra Ponen, Pharmacist. Reviewed By: Assoc Professor Nicola Dalbeth.
Last reviewed: 22 Jan 2018
Here are our answers to the most common questions people ask us about allopurinol.
Frequently asked questions about allopurinol
Starting a new medicine can be worrying, but knowing what to expect and being prepared can be helpful. Here are some common questions people ask about allopurinol.
What are the benefits of taking allopurinol?
Allopurinol is a long-term treatment that prevents gout attacks. It helps to prevent permanent damage to your joints.
What is the best dose of allopurinol for me?
The dose of allopurinol will be different for different people. Your doctor will usually start you on a low dose (50 to 100 milligrams) and increase it very slowly over a few months, until a target serum urate is reached.
Serum urate is measured by a blood test and most people need to aim for a level below 0.36 mmol/L. The usual dose of allopurinol is 300 milligrams or more daily. Doses up to 900 milligrams daily may be needed in some people. Know what dose you should be taking.
What can I expect in the first few days or weeks of starting allopurinol?
When you first start taking allopurinol, you may get stomach upset and nausea (feeling sick). Taking your dose with food may reduce these symptoms.
When you first start taking allopurinol, you may have gout attacks in the first few weeks or months as you are increasing your dose. Your doctor will prescribe additional medication such as a low-dose non-steroidal anti-inflammatory (NSAID) or colchicine to reduces the chances of an attack during this time. Keep taking allopurinol every day, even during a gout attack.
You may get a skin rash or itching (about 2 in every 100 people who take allopurinol will have a skin rash). This can happen anytime while taking allopurinol, but especially in the first few months while increasing the dose. If this happens, stop taking allopurinol and contact your doctor immediately – even if the rash is mild. This can develop into a severe allergic reaction.
How long will I need to take allopurinol?
Allopurinol is a long-term treatment. You will probably need to take allopurinol for the rest of your life. The effects of allopurinol are not immediate. It takes a few weeks or months for allopurinol to lower serum urate to the target level in your blood. Attacks of gout will usually stop during the first year of treatment with allopurinol.
If I am having a gout attack, will an extra dose help?
No. Allopurinol is not a pain reliever and does not take effect immediately. If you have an attack of gout while taking allopurinol, keep taking it at the same dose. Do not stop taking it. Your doctor will advise you to take a pain reliever medicine such as NSAIDs (ibuprofen, diclofenac, naproxen), or steroids such as prednisone or colchicine. You can also apply ice-packs and rest the affected joint, to reduce pain. See your doctor if the pain and inflammation does not improve in 24 hours.
What if allopurinol does not help?
After starting allopurinol, your doctor will monitor your symptoms and your serum urate levels. If after a few months of being on an optimal dose of allopurinol, your symptoms do not improve and your serum urate levels remain high, your doctor may try you on other medicines instead to lower your serum urate such as febuxostat, probenicid or benzbromarone.
What happens if I stop taking allopurinol suddenly?
Do not stop taking allopurinol suddenly unless you have a skin rash or allergic reaction. Speak to your doctor or nurse before stopping. Stopping allopurinol quickly can cause a flare up and make your gout worse.
The following links have more information on allopurinol.