Allopurinol Dosages: Your GoodRx Guide

Allopurinol (Zyloprim) is a first-choice medication option to treat gout. Gout is a type of arthritis (joint inflammation) that can be painful and bothersome. It can cause periods of sudden and intense joint pain, known as gout attacks. But, thankfully, gout is usually very treatable. 

The goal of gout treatment is to prevent future gout attacks and to keep your condition from worsening. Allopurinol is often a useful medication to achieve these goals. To get the most out of your allopurinol prescription, it’s important to take it exactly as prescribed. Here, we’ll cover the most common allopurinol dosages and other useful information.

How does allopurinol work?

Allopurinol treats gout and other conditions by lowering uric acid levels in the body. Uric acid is a natural waste product that forms when the body breaks down purines (chemicals in the body that help build cells). Purines are also found in various foods and drinks. 

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When you have too many purines in the body, you also make too much uric acid, which can lead to conditions like gout. Gout attacks are caused by high amounts of uric acid building up in the joints. This is where allopurinol comes in.

Allopurinol blocks a protein called xanthine oxidase. This prevents your body from making uric acid from purines.  

What’s the typical allopurinol dosage for adults?

Allopurinol comes as a tablet and injection. In this article, we’ll focus on the tablet, which is the most commonly used form. It’s available in 100 mg, 200 mg, and 300 mg strengths and has a three FDA-approved uses:

• Treating gout

• Treating recurrent kidney stones caused by high uric acid levels

• Preventing tumor lysis syndrome

Gout

According to the American College of Rheumatology, allopurinol is a first-choice medication for treating gout.

Usually, your healthcare provider will start your allopurinol dose at 100 mg. Starting at a low dose helps prevent a gout attack, which can occur when you first start taking allopurinol. Your provider may increase your dose every 2 to 5 weeks until your blood uric acid levels are low enough to prevent gout attacks, usually 6 mg/dL or less. This may take many weeks to achieve.

Your allopurinol dosage will depend on how high your uric acid levels are. For mild gout, most people take between 200 and 300 mg of allopurinol per day. For more severe gout, you may need 400 to 600 mg daily. If you need more than 300 mg, it’s usually divided into two doses per day.

The maximum allopurinol dose is 800 mg per day, even if target uric acid levels haven’t been attained. In this case, another medication to treat gout may be needed.

Tumor lysis syndrome prevention

Tumor lysis syndrome is a medical emergency that can be caused by chemotherapy treatments. This condition is usually only a concern with fast-growing cancers. As cancer cells die during chemotherapy treatment, uric acid and other chemicals may spill out from your cells and into your bloodstream. This can result in significant organ damage. 

To prevent the high uric acid levels caused by certain chemotherapies, you may receive a few doses of allopurinol shortly before your treatment. It may be administered in the tablet form or through an IV. The usual allopurinol dosage for this purpose is 600 to 800 mg daily, which should be taken along with plenty of fluids. The type of chemotherapy you’re receiving will determine when you’ll start taking allopurinol and how long you’ll take it. It’s common to start the medication 2 to 3 days prior to chemotherapy and continue for at least 10 to 14 days.

Recurrent kidney stones caused by high uric acid

The usual allopurinol dosage to prevent recurrent kidney stones is 200 to 300 mg per day. You can take this as one dose or divided into two doses. Your healthcare provider may check uric acid levels in your urine and adjust your dose based on these levels.

What’s the typical allopurinol dosage for children?

Allopurinol can help prevent tumor lysis syndrome in certain children with cancer. Children who are 6 to 10 years old may receive 300 mg per day. The dose may be adjusted based on blood uric acid levels.

Though it’s not approved for children under 6, some guidelines and studies do recommend allopurinol to prevent tumor lysis syndrome in this population. The dose is based on weight.

Are there any dosage adjustments for medical conditions?

Allopurinol is filtered out through your kidneys and leaves the body through your urine. So if your kidneys aren’t working normally, allopurinol may build up in the body and cause side effects. 

If you have any kidney problems (such as chronic kidney disease) before starting allopurinol, your healthcare provider will likely start you at a lower dose than usual. This may be less than 100 mg daily. Your dose may be increased slowly based on your uric acid levels.

Keep in mind: Before starting allopurinol, make sure your healthcare provider and pharmacist know about any other medications you take. Other medications can increase levels of allopurinol in the body and make side effects more likely. Allopurinol can also increase the levels of some other medications in your body. For example, allopurinol can significantly increase levels of mercaptopurine (Purinethol) and azathioprine (Imuran). If you’re taking allopurinol, your dosage of these drugs may be reduced by as much as 75%.

Are there any specific instructions for taking allopurinol?

Allopurinol can be taken with or without food. But it's best taken after meals to help prevent stomach upset.

While taking allopurinol, it’s important to stay hydrated. Dehydration can worsen gout.

What happens if you miss a dose of allopurinol?

If you miss a dose of allopurinol, take it as soon as you remember. However, if it’s almost time for your next dose of allopurinol, just skip the missed dose and wait for your next one. Never take two doses at once.

What should you do if you take too much allopurinol?

Taking too much allopurinol can lead to serious side effects, including a severe rash, liver problems, and abnormal blood cell levels. Allopurinol toxicity may be more likely if you have existing kidney problems, because your body will have a harder time getting rid of allopurinol.

In the case of an allopurinol overdose, seek emergency care.

How to save on allopurinol

Allopurinol is available as both a brand-name and lower-cost generic medication. GoodRx can help you save over 70% off the average retail price of the generic version. Generic allopurinol at certain pharmacies is as low as $4.80 with a free GoodRx discount.

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Written by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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