Allopurinol (Zyloprim, Aloprim)


Allopurinol is a medication used to prevent gout attacks. It works by reducing the amount of uric acid your body makes, which then lowers it in the blood. After several months of low uric acid levels, the uric acid crystals dissolve, reducing the risk of gout attacks. However, while uric acid crystals are dissolving, the risk of gout attacks increases for a few months. To prevent gout attacks in the first few months of taking allopurinol, anti-inflammatory medications such as colchicine and NSAIDs may be added until the risk decreases.

How to Take It

Allopurinol is usually taken in the morning with food and water. Because dehydration can worsen gout it is important to stay hydrated while taking allopurinol. Allopurinol lowers uric acid levels within a few days; however, it may take up to 6 months before crystallized uric acid dissolves. For most people the goal of their uric acid level blood test is less than 6 mg/dL. Allopurinol is usually started at low dose and increased over time to reach an acceptable uric acid level.

Some patients (those of Southeast Asian or African descent) may have a genetic predisposition to allergic reactions to the allopurinol in this medication, and your provider may check a genetic marker (HLA- B5801) before starting.

Side Effects

The most significant side effect for allopurinol is the risk of an allergic reaction. This risk is rare. If you develop any skin itching, rashes, or hives, you should discontinue allopurinol immediately and inform your provider. Allopurinol is safe to use in chronic kidney disease but start doses must be low and slowly increased over time.

Tell Your Rheumatology Provider

You should notify your rheumatology provider if you have a history of liver or kidney disease. Also, let your rheumatology provider know if you have ever had or developed a reaction to allopurinol, particularly a skin rash or allergic reaction. Make sure to notify your other physicians while you are taking this drug, especially if you are taking azathioprine or 6-mercaptopurine. If you are pregnant or considering pregnancy, let your doctor know before starting this medication. Women should discuss birth control with their primary care physicians or gynecologists. Breast-feeding should be avoided while taking allopurinol. The risk in pregnancy and breastfeeding has not been determined.

Updated March 2023 by Howard Yang, MD, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.

This patient fact sheet is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.

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