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Allopurinol for Chronic Gout

What You Need to Know About Allopurinol


Updated June 27, 2014

Allopurinol (which goes by the brand names Aloprim and Zyloprim) is a drug that belongs to a class of medications called xanthine oxidase inhibitors. Allopurinol is prescribed for the treatment of chronic gout and is used to prevent rather than treat gout attacks.

The medication works by blocking uric acid production. Uric acid is a waste product normally present in the blood as a result of the breakdown of purines. Excessive amounts of uric acid can cause crystals to form in the joints, which can lead to gout.

When is allopurinol prescribed?

Allopurinol is prescribed to prevent chronic gout attacks, manage high uric acid levels caused by cancer medications, and treat kidney stones. There are also a handful of off-label uses for which your doctor may prescribe allopurinol.

What is the availability of allopurinol?

Allopurinol is available as a 100 mg. tablet. It is taken once or twice daily, usually following a meal.

Are there any special instructions regarding how to take allopurinol?

Patients are advised to follow the prescribing instructions precisely. It is common for the starting dose of allopurinol to be low and gradually increased. Noticeable benefit from taking allopurinol may take months. In fact, during the first few months of use, the medication may actually increase the number of gout attacks. Eventually, allopurinol will prevent gout attacks. In the interim, colchicine may be prescribed as well. Do not stop taking allopurinol even if you're feeling well.

Are there patients who should not take allopurinol?

Patients who are known to be allergic to allopurinol obviously should not take the medication. Patients taking any of the following medications should tell their doctor because they may require a dose adjustment:

  • Amoxicillin
  • Ampicillin
  • Coumadin
  • Cytoxan
  • Purinethol
  • Diabinese
  • Diuretics
  • Immunosuppressants
  • Other gout medications

What common side effects can occur with allopurinol?

Allopurinol can cause upset stomach, diarrhea, and drowsiness. Rash is one of the more common side effects and can occur even after months or years of treatment with allopurinol.

Are there more severe side effects associated with allopurinol?

Uncommon side effects that are more severe if they occur include:

  • Hypersensitivy reactions
  • Itching
  • Blood in urine or pain when urinating
  • Eye irritation
  • Swelling around mouth or lips
  • Signs of infection
  • Loss of appetite or unexpected weight loss

What special warnings and precautions are associated with allopurinol?

Patients are advised to drink 8 glasses of water daily (unless a doctor instructs otherwise). Alcoholic drinks may decrease the effectiveness of allopurinol. Drinks or supplements containing vitamin C may be problematic in large quantities. Excessive vitamin C and allopurinol can combine to make urine acidic and cause kidney stones. Patients with kidney problems may need dose adjustment for allopurinol.

Are there special instructions for pregnant or nursing women?

If you are pregnant, breastfeeding, or planning on becoming pregnant, discuss allopurinol with your doctor. Few reports of allopurinol use during pregnancy exist. Although no adverse fetal outcomes associated with allopurinol have been noted in humans, allopurinol should only be used after weighing benefit to the patient versus risk to the fetus.

How is it determined that allopurinol is an effective treatment?

Certain laboratory tests are periodically ordered which help to determine if the drug is working effectively.


Allopurinol. The Cleveland Clinic Information Center. 4/15/2003.

Allopurinol. Merck Manual Davis's Drug Guide. May 2007.

Drug Information: Allopurinol. MedlinePlus. 7/1/2003.

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