Zyloprim (Allopurinol) - Oral

What Is Zyloprim?

Zyloprim (allopurinol) is an oral prescription drug used to help prevent arthritis flares and other symptoms from a disease called gout. It is taken in the form of a pill.

Zyloprim is a urate lowering therapy (ULT), part of a class of drugs known as xanthine oxidase inhibitors. ULTs are important for the management of gout.

In people with gout, certain types of crystals (monosodium urate crystals) form in one or more joints abnormally. These cause inflammation and periodic attacks of painful joint symptoms. One of the main reasons this happens is because a substance called uric acid is present at higher-than-normal levels in your blood.

Uric acid is a normal waste product in your body, produced by the breakdown of purines (a natural substance in your body and in many foods you eat). Zyloprim blocks a certain enzyme that is important for breaking down these purines. Other ULTs can work in different ways, such as increasing the amount of uric acid released through your urine.

Drug Facts

Generic Name: Allopurinol

Brand Name(s): Zyloprim

Administration Route(s): Oral

Drug Availability: Prescription

Therapeutic Classification: Antigout

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Allopurinol

Dosage Form(s): Tablet

What Is Zyloprim Used For?

The Food and Drug Administration (FDA) approved Zyloprim to treat gout.

Zyloprim is often prescribed for primary gout—gout that doesn’t have another medical cause. However, it can also treat gout symptoms due to other diseases (secondary gout). For example, certain therapies used to treat leukemia may cause elevations in uric acid levels, which can cause symptoms of gout. These people might need treatment with Zyloprim.

Other conditions that can cause symptoms of gout include:

Additionally, Zyloprim is helpful for some people who have recurrent kidney stones, specifically calcium oxalate type of stones.

The American College of Rheumatology, an organization of health professionals focused on treating rheumatic diseases, recommends ULTs for all gout patients, even with infrequent flares. It is especially important for people who have the tophaceous variety of gout or for people who have joint damage that can be seen on an x-ray.

How to Take Zyloprim

Swallow Zyloprim tablets with water and drink plenty of water throughout the day. Ideally, take the medication after having some food to minimize any potential stomach discomfort. It doesn’t matter when you take it, but you should take it at the same time each day. If you are on a large dose, you might need to take it more than once a day.

Your prescriber may instruct you to take a nonsteroidal anti-inflammatory drug or an anti-inflammatory medication called colchicine when initiating allopurinol therapy to manage potential flare-ups.


Verywell / Zoe Hansen


Store allopurinol tablets at room temperature, away from heat and light.

Off-Label Uses

Allopurinol is sometimes used off-label for some health conditions that it is not indicated to treat but has shown benefits for.

For example, healthcare providers sometimes prescribe allopurinol to help prevent organ rejection in people who have had kidney transplants.

Other potential off-label uses include:

How Long Does Zyloprim Take to Work?

It may take a while to feel the full effects of Zyloprim. Zyloprim can take several weeks before it reaches peak levels in the body.

You may still have flares when you first start taking it. However, over time, Zyloprim will reduce the number of flares you have.

What Are the Side Effects of Zyloprim?

This is not a complete list of side effects and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 1-800-FDA-1088.

Like other medications, Zyloprim can cause side effects. Talk to your healthcare provider about any side effects you experience while taking this medication, especially if they worsen or don't go away.

Common Side Effects

Typically, starting Zyloprim doesn’t cause any side effects.

Although not common, one of the most frequent side effects is an increase in painful gout attacks for a limited time. However, this seems to happen in less than 1% of people. It is also less likely to happen if you start with a low prescribed dose and gradually increase the amount you take. Taking colchicine or another anti-inflammatory drug at the same time, for at least a few months, may also prevent this side effect.

Other side effects may include:

  • Drowsiness
  • Upset stomach
  • Diarrhea

Severe Side Effects

In rare cases, Zyloprim may cause a rash. If that happens, your healthcare provider will likely want you to stop taking the drug. A rash might signify potentially severe and even life-threatening reactions that can affect multiple organ systems. The drug may cause a serious allergic reaction.

Zyloprim has caused severe kidney problems. However, this seems to be much more likely in people with certain medical conditions, such as multiple myeloma or congestive heart disease. Very rarely, Zyloprim might damage your liver.

Call your healthcare provider if you have any potentially severe symptoms, such as:

  • Skin rash
  • Blood in your urine
  • Painful urination
  • Fever 

If you have any potentially life-threatening symptoms, like difficulty breathing, call 911 for immediate care.

Report Side Effects

Zyloprim may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Zyloprim Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For gout:
      • Adults—At first, 100 to 300 milligrams (mg) per day, taken once a day or in divided doses. Your doctor may adjust your dose as needed. However, the dose is usually not more than 800 mg per day.
      • Children—Use and dose must be determined by your doctor.
    • For high uric acid levels caused by cancer medicines:
      • Adults and children 11 years of age and older—600 to 800 milligrams (mg) per day, taken in divided doses for 2 to 3 days.
      • Children 6 to 10 years of age—300 mg per day, taken once a day for 2 to 3 days.
      • Children younger than 6 years of age—150 mg per day, taken once a day for 2 to 3 days.
    • For kidney stones:
      • Adults—200 to 300 milligrams (mg) per day, taken once a day or in divided doses. Your doctor may adjust your dose as needed. However, the dose is usually not more than 800 mg per day.
      • Children—Use and dose must be determined by your doctor.


Depending on the context, your healthcare provider might prescribe you a lower dose of medication. For example, people with decreased kidney function require lower doses of Zyloprim.

Monitoring Serum Urate

You will likely start on a low dose of allopurinol at first and gradually increase your dose over time.

Your healthcare provider will monitor your symptoms and regularly check a blood test, called a serum urate (SU) or uric acid test. This test measures the amount of uric acid in your blood. Your provider will target a certain amount in your blood. In other words, your dose may continue to increase until your uric acid levels are low enough to help prevent future gout attacks.

Missed Dose

If you miss a dose, take it as soon as possible. It won’t be a big deal if you miss a dose, but try to take the drug exactly as prescribed. Do not double-up on your doses if it is very close to the next time you are scheduled to take it.

Overdose: What Happens If I Take Too Much Zyloprim?

Accidentally taking an extra dose of Zyloprim is unlikely to be harmful. It is not an incredibly toxic drug, and massive overdosing or acute poisoning of Zyloprim has not been reported. However, it’s reasonable to be cautious.

What Happens If I Overdose On Zyloprim?

If you think you or someone else may have overdosed on Zyloprim, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Zyloprim, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your or your child's progress at regular visits to make sure that this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

When you start using this medicine, you may have more gout attacks. Keep using the medicine even if this happens. Your doctor may give you other medicines (eg, colchicine, pain medicines [NSAIDs]) to help prevent the gout attacks.

Serious skin reactions can occur with this medicine. Call your doctor right away at the first appearance of a skin rash or allergic reaction (eg, trouble breathing or swallowing, swelling of your hands, face, or mouth). Check with your doctor if you also develop blistering, peeling, or loosening of the skin, red skin lesions, severe acne, or sores or ulcers on the skin.

Check with your doctor right away if you or your child have stomach pain or tenderness, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of a serious liver problem.

This medicine may cause some people to become drowsy or less alert than they are normally. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Zyloprim?

People with certain medical conditions should be cautious when taking Zyloprim.

For example, kidney or liver disease may increase the risks of Zyloprim. You may need more monitoring, such as blood tests that check how your liver is doing.

Under most circumstances, you should not use Zyloprim during pregnancy. Anyone breastfeeding should also be cautious. If you plan to breastfeed while taking Zyloprim, discuss the risks and benefits with your healthcare provider.

Anyone who has ever had an allergic reaction to Zyloprim should avoid taking it.

It is not recommended that you take Zyloprim if you have high uric acid levels (as found on a blood test) but no symptoms.

What Other Medications Interact With Zyloprim?

Be sure to tell your healthcare provider about all the medications you take, including over-the-counter products and herbal treatments. In some cases, these medications might interfere with how well and how safely Zyloprim works. You might need to adjust your dose or avoid Zyloprim altogether if you are taking certain medications.

It is not recommended to use Zyloprim with Videx (didanosine), a medication used to treat HIV.

Other medications that interact with Zyloprim include:

  • Anticoagulants, such as warfarin
  • Some antibiotics, such as Amoxil (amoxicillin)
  • Cancer chemotherapy drugs, like Cytoxan (cyclophosphamide)
  • Diuretic drugs, like Diuril (chlorothiazide)
  • Medications that suppress the immune system, like Imuran (azathioprine)

What Medications Are Similar?

Other medications are sometimes prescribed instead of allopurinol to help lower uric acid levels in people with gout, such as Uloric (febuxostat) and Benemid (probenecid). These medications are given instead of allopurinol, not in addition to it.

Like allopurinol, febuxostat is a xanthine oxidase type of drug that lowers the amount of uric acid in your body. However, healthcare providers usually prefer to prescribe allopurinol. Although the science on this is evolving, research suggests that febuxostat might not be as safe as allopurinol, especially for people with existing heart problems. Additionally, allopurinol is less expensive.

Probenecid is another potential option. Some data suggest that it may be even safer than allopurinol in terms of heart attack and stroke risk. But it may not be a good choice if you have kidney disease.

Other drugs may be used in gout as well. For example, anti-inflammatory drugs, such as colchicine, can help prevent flares (especially when you first start taking allopurinol). They also reduce pain from any flares that do happen. These should be used in addition to a drug that lowers uric acid levels (like allopurinol).

Frequently Asked Questions

  • When will Zyloprim start to work?

    Zyloprim takes a while to work. It can take several weeks before the drug reaches its optimal level. Also, your healthcare provider might not start you on the full dose you will eventually need, but will instead increase your dose gradually.

  • Can I take other drugs for gout in addition to Zyloprim?

    Many people taking allopurinol will also need to take an anti-inflammatory drug. This is most likely necessary during the first three to six months after you start taking allopurinol. Doing so will decrease your risk of getting symptoms from gout during this time. These drugs can also be used temporarily for someone who is experiencing a flare of their gout joint symptoms.

  • What should my serum urate be?

    You will probably need repeated serum urate (SU) blood tests while taking allopurinol, at least for a while. These measure the amount of uric acid in your blood. It’s this uric acid that can form crystals in your joints and trigger symptoms.

    For most patients, it is recommended to target an SU level of less than six milligrams per decilitre. If your number is higher than this, you might need to start taking a higher dose.

  • Do I need to keep taking Zyloprim if my symptoms are gone?

    Yes. Zyloprim does not cure the problem that caused gout in the first place. If you stop taking the drug, those symptoms are likely to come back.

How Can I Stay Healthy While Taking Zyloprim?

Zyloprim is a very safe medication that can help you dramatically reduce your symptoms from gout. However, Zyloprim can take some time to work, so have patience. Work with your healthcare provider to get lab testing of your uric acid levels to determine the best dose for you.

Diet can also play an important role in managing gout symptoms. Foods that are high in purines (a chemical compound that creates uric acid when metabolized) can trigger attacks. Eating nutritious, low-purine foods can help your body eliminate uric acid and better manage symptoms.

Foods that make gout symptoms worse include:

  • Red meat
  • Organ meats
  • Coldwater fish
  • Beer, liquor
  • Sugary foods and beverages

On the other hand, foods such as vegetables, low-fat dairy, whole grains, citrus fruits, and cherries can help manage your condition.

Following your healthcare provider’s other instructions—like drinking plenty of water and avoiding certain foods—will help you lower your risk of painful, gouty joints.

Medical Disclaimer

Verywell Health's drug information is meant for education purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Zyloprim (allopurinol) product information.

  2. Ragab G, Elshahaly M, Bardin T. Gout: An old disease in new perspective - A reviewJ Adv Res. 2017;8(5):495-511. doi:10.1016/j.jare.2017.04.008

  3. FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology guideline for the management of gout. Arthritis Care Res (Hoboken). 2020 Jun;72(6):744-760. doi:10.1002/acr.24180

  4. Osadchuk L, Bashir MH, Tangirala B, et al. Effect of allopurinol on slowing allograft functional decline in kidney transplant recipients. Exp Clin Transplant; 12(3):190-4.

  5. National Institutes of Health. MedlinePlus. Allopurinol.

  6. Kim SC, Neogi T, Kang EH, et al. Cardiovascular risks of probenecid versus allopurinol in older patients with gout. J Am Coll Cardiol. 2018 Mar 6;71(9):994-1004. doi:10.1016/j.jacc.2017.12.052

By Ruth Jessen Hickman, MD
Ruth Jessen Hickman, MD, is a freelance medical and health writer and published book author.