Allopurinol Helps to Prevent Gout Attacks

Treatment Option for People With Chronic Gout

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Allopurinol (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 to treat kidney stones. There are also a handful of off-label uses for which your doctor may prescribe allopurinol.

What Is the Usual Dosage of Allopurinol?

Allopurinol is available as a 100 mg tablet. It is typically taken once or twice daily, usually following a meal. The dose may be increased gradually at weekly intervals in increments of 100 mg/day as needed to achieve the optimal serum uric acid level. Usual dosage range is 200 to 300 mg/day for mild gout; 400 to 600 mg/day for moderate to severe tophaceous gout. The maximum daily dose is 800 mg/day.

Are There Special Instructions?

People 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 should be prescribed to reduce the risk of gout attack. Do not stop taking allopurinol even if you're feeling well.

Should Some People Not Take Allopurinol?

People with a known allergy to allopurinol obviously should not take the medication. People who take 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

Allopurinol has been associated with hypersensitivity reactions, especially in certain populations, such as  Koreans with stage 3 or worse chronic kidney disease, Han Chinese, and people of Thai descent. People with suspected hypersensitivity in the aforementioned populations can be tested for HLA-B*5801 prior to initiating treatment with allopurinol. 

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 Severe Side Effects Associated With Allopurinol?

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

  • Hypersensitivity 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?

People are advised to drink plenty 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 a 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 Effectiveness of Allopurinol Assessed?

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


Drug Information: Allopurinol. MedlinePlus. Revised 02/11/2012.

Allopurinol: Drug Information. Lexicomp. Accessed 06/17/2016.

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