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Allopurinol - What is it for

It is used to lower uric acid levels in the body by preventing its formation. This is expected to bring forth the following benefits:

  • Long-term prevention of gout attacks
  • Prevention of kidney stone, especially if the serum uric acid levels are elevated
  • Dissolution of 'big' uric acid crystal called tophus
  • Preventing serum uric acid levels from going up too high during chemotherapy

Your doctor may also give it to you for reasons other than what have been mentioned above e.g. Lesch-Nyhan Syndrome.

Allopurinol - Side Effects, Precautions, and Contraindications

What side effects can Allopurinol cause?

The medication is generally well-tolerated. The most common side effects are:

  • Loose stools (diarrhea)
  • Stomach upset
  • Drowsiness (reported by patients occasionally but not common). Avoid driving or operating heavy machinery if it occurs

Before taking Allopurinol, what precautions must I follow?

What food or medicine must I avoid when I take Allopurinol?

Allopurinol - Dosage and How to Use

How should Allopurinol be used?

Your doctor would normally start it at a low dose and gradually increase the dose if necessary (typically based on the uric acid concentration in the blood). This helps to make you tolerate the medication better and lessens the likelihood of the gout flares initially.

Be patient and take it at the dose recommended by your doctor. The benefits are slow to come so do not discontinue the medication unless skin rashes as detailed above occur.

Take it after meals at the same time every day. Do drink plenty of non-caffeinated/non-carbonated fluids throughout the whole day, especially during the early part of the day, unless your doctor tells you to restrict fluid intake. This is especially important if you have a history of kidney stones as adequate fluid intake may help to dissolve existing or prevent new stone formation.

What should I do if I miss a dose?

If you forget to take you medication at the usual time, you can take it as soon as you remember about it. But if it is near the time for the next dose when this happens, just skip the missed dose and take the next dose as usual. Do not take more than the usual scheduled dose to make up for the missed dose.

What should I do if I overdose?

Allopurinol - Handling

How should I handle Allopurinol safely?

Allopurinol - Storage

How should I store Allopurinol?

Keep away from children;#Keep in a cool, dry place, away from direct sunlight;#

How should I dispose of Allopurinol safely?

Allopurinol - Additional Information

How LONG does it take for the medicine to be EFFECTIVE?

  • It usually takes months to notice any improvement in symptoms after starting allopurinol.
  • The frequency of gout attack may increase in the first few weeks or months after the initiation of this medication.
  • However, in the long run the use of allopurinol may prevent gout flares and/or result in the dissolution of uric acid deposits called tophi.
  • There are measures that can be taken to prevent or lessen the impact of the gout flares such as the concurrent use of low-dose colchicine or non-steroidal anti-inflammatory drugs (NSAIDs) for the first few months. You may want to ask your doctor about it.

When do I seek medical attention IMMEDIATELY?

  • As with any other medications, a very small number of patients using allopurinol may experience RARE but serious side effects. Do seek medical attention if you develop:
  • Any skin rashes as serious allergic reactions involving the skin and mucous membrane of the mouth, nose, throat and genitals have been reported. In extreme cases, extensive skin peeling and ulceration of the mucous membranes may occur. Normally, these reactions are preceded by flu-like symptoms such as fever, headache and body ache. These reactions may happen immediately after treatment or sometimes delay after a month after allopurinol is started.


  • Your doctor may prescribe pain-relieving treatments to reduce inflammation and pain quickly and to prevent gout flare during the initial treatment.
  • Always check with the doctor or pharmacist first before self-treatment with any over-the-counter medicines.
  • DO NOT take any supplements, alternative or herbal medicines without informing your doctor or pharmacist.

What special DIETARY instructions should I follow?

  • Maintain adequate hydration (2 - 3 liters of fluid a day, unless otherwise advised by your doctor).


  • Please tell your doctor if you are breast-feeding, pregnant or likely to become pregnant during the course of treatment with the medication.

In SUMMARY… what you need to know about allopurinol?

  • Take allopurinol approximately at the same time every day, unless instructed otherwise by your doctor.

  • Always come for your BLOOD TESTS on the scheduled date.

  • Beware of the SIDE EFFECTS and when to get immediate medical attention.

  • Never take medicines, supplements or herbal treatments OVER-THE-COUNTER without checking with your doctor or pharmacist first.

  • If you have further questions about Allopurinol, please call ______________________ (office number) to discuss with your doctor / pharmacist / specialty nurse (please circle as appropriate).
  • Updated on Friday, June 12, 2015
  • Article contributed by Pharmacy, Rheumatology & Immunology Singapore General Hospital

    The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

    A Health Sciences Authority (HSA) consumer guide is also available for this drug. These consumer guides provide simple, everyday tips on how you can further protect yourselves against unwanted side effects or reactions when using products ranging from western medicines to health supplements to cosmetics.

    For more information, visit the HSA consumer guide on Allopurinol.

    Information provided in the PDF is extracted directly from the source. SingHealth does not alter or vet the content. Please use the information on user's own discretion. Consult your doctor or pharmacist for relevant information.

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