Examples

Allopurinol is taken in tablet form (oral). It is taken in low dosages at first. The dosage is gradually increased to control uric acid levels.

How It Works

Allopurinol prevents the release of a substance called xanthine oxidase, which helps in the formation of uric acid. In treatment for gout, allopurinol blocks the production of uric acid in the body.

Why It Is Used

Allopurinol may be prescribed to prevent gout attacks. It also may be used because of:

• Overproduction of uric acid.
• Frequent gout attacks.
• Presence of gritty, chalklike clumps of uric acid crystals (tophi).
• Failure of other medications to adequately reduce uric acid levels.
• Allergy to uricosuric medications, which increase the elimination of uric acid. Uricosuric medications include probenecid (Benemid) and sulfinpyrazone (Anturane).
• Poor kidney function.
• History of uric acid kidney stones.

Allopurinol may also be used for the prevention of kidney disease in people going through medication treatment for cancer.

The dose of allopurinol may need to be lower for people who have chronic kidney disease or are taking azathioprine.

Allopurinol is not recommended for people who:

• Have a known sensitivity to allopurinol.
• Have a condition in which there is too much iron in the body (hemochromatosis).

Allopurinol should not be started for the first time by people who are still having symptoms caused by a gout attack.

How Well It Works

Allopurinol can lower uric acid levels to normal in about 2 to 4 weeks and should reduce the frequency of gout attacks.¹ After the proper dose is reached, the uric acid levels should return to normal. Your health professional will monitor your uric acid level within one month of starting or changing a dose of allopurinol.

Treatment with allopurinol can reduce the size of tophi.

Side Effects

Skin rash is a common side effect. Because a skin rash may be a symptom of an allergic reaction to allopurinol, have your health professional evaluate any skin rash that develops while you are taking this medication.

Rare, serious side effects include:

• Inflammation of the liver (hepatitis).
• Failure of bone marrow to produce blood cells (aplastic anemia).
• Inflammation of blood vessels (vasculitis).
• Allopurinol hypersensitivity syndrome (a widespread rash, fever, mouth sores, poor kidney function, liver inflammation, and other complications), which can be life-threatening.

Allopurinol interferes with many other medications. It may increase or decrease the levels of other medications, which may increase the toxicity of these medications or reduce their effectiveness.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

• Allopurinol should not be used until the symptoms of a gout attack are gone. However, if you are already taking allopurinol, continue to take it (even during an attack).
• Gout attacks may increase at first for some people taking allopurinol. To avoid this, doctors may prescribe colchicine, which blocks the inflammation caused by uric acid crystals, or low-dose nonsteroidal anti-inflammatory drugs (NSAIDs) to be taken at the same time. After normal uric acid levels have been maintained for 6 to 12 months and no further attacks occur, colchicine or NSAIDs do not need to be taken.
• Because of the rare risk of serious side effects, many doctors may prefer uricosuric medications to allopurinol.
• Laboratory studies, including a complete blood count (CBC) and liver and kidney function studies, may be done after a few months of using allopurinol. Studies may then be repeated every year in otherwise healthy people or more frequently in people with other medical problems.

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Citations

1. Wortmann RL, Kelley WN (2005). Gout and hyperuricemia. In ED Harris Jr et al., eds., Kelley's Textbook of Rheumatology, 7th ed., pp. 1402–1429. Philadelphia: Elsevier Saunders.