What does allopurinol do for gout?

Allopurinol is used to prevent gout. Find out how to take it safely and possible side effects.

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.

Watch a video about allopurinol for gout. 

How does allopurinol work?

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 as gout.

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.

Dose 

• 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.

What are the side effects of allopurinol?

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.

Interactions

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.

Learn more

The following links have more information on allopurinol.

Allopurinol Rheuminfo
Allopurinol (Māori) NZ Formulary Patient Information
Medicines for gout Ministry of Health, NZ
A conversation about gout (includes dispelling common myths including gout is a bad drug) BPAC, NZ
Out with gout Pharmac, NZ

References

1. Allopurinol NZ Formulary
2. Managing gout in primary care – part 1 BPAC 2018
3. Managing gout in primary care – part 2 BPAC 2018

Additional resources for healthcare professionals

DP-Allopurinol Medsafe, NZ
DRESS syndrome – remember to look under the skin Medsafe, NZ, 2011
Case report – Stevens-Johnson syndrome associated with the use of allopurinol Medsafe, NZ, 2010
Allopurinol - safe prescribing - dose up SafeRx, NZ, 2019
Gout - Nicola Dalbeth Goodfellow Podcast, NZ, 2016
A conversation about gout (includes dispelling common myths including gout is a bad drug) BPAC, NZ, 2014

The Māori Pharmacists’ Association Ngā Kaitiaki o Te Puna Rongoā has a free phone line to answer questions whānau have about their medicines. Call 0800 664 688.

Note: This is a non-urgent service and they will get back to you within 24 hours.
For urgent health advice freephone Healthline 0800 611 116.

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