Allopurinol | Side Effects, Dosage, Uses & More
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Generic Name:

allopurinol, Oral tablet

All Brands

  • Zyloprim
SECTION 1 of 5

Highlights for allopurinol

Oral tablet
1

Allopurinol is used to treat gout, elevated serum uric acid levels, and recurrent kidney stones.

2

This drug comes in the form of a tablet you take by mouth. It’s also given as an injection you receive in the hospital by a healthcare provider. 

3

Allopurinol is available as brand-name drugs called Xyloprim and Lopurin. It’s also available as a generic drug.

4

The more common side effects of this drug include skin rash, diarrhea, nausea, and changes in your liver function test results. If you have gout, this drug may also cause gout flare-ups.

5

In some cases, allopurinol can cause serious side effects. These can include severe skin rash and liver injury.

IMPORTANT INFORMATION

Severe skin rash

This drug may cause a severe, life-threatening skin rash. If you have itchiness, trouble breathing, or swelling of your face or throat, stop taking this drug and call your doctor right away.

Liver injury

This drug may cause changes in liver function test results and liver failure. This may be fatal. If you develop liver problems, your doctor may have you stop taking allopurinol.

Drowsiness

This drug can cause drowsiness. You shouldn’t drive, use machinery, or do other tasks that require alertness until you know how it affects you.

Fluid intake

You should drink at least 3.4 liters (14 cups) of fluids each day. This will help you urinate at least 2 liters (2 quarts) per day. This can help prevent sharp, uric acid crystals from forming and blocking your urine flow. Ask your doctor how to measure how much you urinate.

What is allopurinol?

Allopurinol is a prescription drug. It’s available as an oral tablet. It’s also available in an intravenous (IV) form, which is only given by a healthcare provider.

Allopurinol is available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version. Talk to your doctor to see if the generic version will work for you.

Allopurinol may be used as part of a combination therapy. This means you may need to take it with other medications.

Why it's used

Allopurinol is used to decrease uric acid levels in the blood and urine in people with high uric acid levels.

How it works

Allopurinol belongs to a class of drugs called xanthine oxidase inhibitors.

More Details

Why it's used

Allopurinol is used to decrease uric acid levels in the blood and urine in people with high uric acid levels. 

High uric acid may be caused by the following:

  • Gout. In this condition, uric acid builds up and can cause severe pain, redness, and swelling in your joints. 
  • Kidney stones, kidney damage, or dialysis
  • Cancer chemotherapy
  • Psoriasis (scaly, itchy, dry skin patches)
  • Use of diuretics (water pills)
  • A diet high in soft drinks, beef, steak, salami, or beer

How it works

Allopurinol belongs to a class of drugs called xanthine oxidase inhibitors. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Allopurinol decreases blood and urine uric acid levels by blocking xanthine oxidase. This is an enzyme that helps make uric acid. High levels of uric acid in your blood or urine can cause gout, a painful form of arthritis, or kidney stones.

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SECTION 2 of 5

allopurinol Side Effects

Oral tablet

More Common Side Effects

The more common side effects of allopurinol can include:

  • skin rash

  • diarrhea

  • nausea

  • changes in your liver function test results

  • gout flare-up (if you have gout)

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

Call your doctor right away if you have serious side effects. Call 9-1-1 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Severe skin rash. Symptoms can include:

    • itchy hives (raised bumps on your skin)
    • red or purple-colored spots on your skin
    • scaly skin
    • fever
    • chills
    • trouble breathing
    • swelling of your face or throat
  • Liver injury. Symptoms can include:

    • tiredness
    • lack of appetite
    • weight loss
    • right upper abdominal area pain or discomfort
    • jaundice (dark-colored urine or yellowing of your skin or the whites of your eyes)
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Allopurinol may cause drowsiness. You shouldn’t drive, use machinery, or do other tasks that require alertness until you know how allopurinol affects you.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 5

allopurinol May Interact with Other Medications

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Allopurinol can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Medications that might interact with this drug

Interactions that increase your risk of side effects
  • Side effects from allopurinol: Taking allopurinol with certain medications raises your risk of side effects from allopurinol. This is because the amount of allopurinol in your body is increased. Examples of these drugs include:
    • Ampicillin or amoxicillin. You may have an increased risk of a skin rash. 
    • Thiazide diuretics, such as hydrochlorothiazide. You may have an increased risk of allopurinol side effects. These include skin rash, diarrhea, nausea, changes in your liver function test results, and gout flare-ups.
  • Side effects from other drugs: Taking allopurinol with certain medications raises your risk of side effects from these drugs. Examples of these drugs include:
    • Mercaptopurine. Allopurinol can increase the blood levels of mercaptopurine in your body. It does this by blocking one of the enzymes used to break down mercaptopurine. This can cause severe side effects from mercaptopurine. Your doctor may  reduce your mercaptopurine dose.
    • Azathioprine. Allopurinol can increase the blood levels of azathioprine in your body. It does this by blocking one of the enzymes used to break down azathioprine. This can cause severe side effects from azathioprine. Your doctor may  reduce your azathioprine dose.
    • Dicumarol. Allopurinol may cause dicumarol to stay in your body longer. This can increase your risk of bleeding.
    • Chlorpropamide. Allopurinol may cause chlorpropamide to stay in your body longer. This can raise your risk of low blood sugar.
    • Cyclosporine. Taking allopurinol with cyclosporine may increase cyclosporine levels in your body. Your doctor should monitor your cyclosporine levels and adjust your dose if needed.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
Allopurinol warnings
kidney problems
People with kidney problems

If you have kidney problems or a history of kidney disease, you may not be able to clear this drug from your body well. This may increase the levels of allopurinol in your body and cause more side effects. This medication may also decrease your kidney function. This would make your kidney disease worse.

pregnant women
Pregnant women

Allopurinol is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used if the potential benefit justifies the potential risk to the fetus.

breastfeeding
Women who are breast-feeding

Allopurinol passes into breast milk and may cause side effects in a child who is breast-fed.

Talk to your doctor if you breast-feed your child. You may need to decide whether to stop breast-feeding or stop taking this medication.

for seniors
For seniors

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

for children
For children

This medication hasn’t been studied and shouldn’t be used in people younger than 18 years for the treatment of gout or kidney stones.

call doctor
When to call the doctor

Call your doctor right away if you become pregnant while taking this drug.

Call your doctor if your symptoms of gout get worse while you’re taking this drug. When you first start taking this medication, it can cause your gout to flare up. Your doctor may give you nonsteroidal anti-inflammatory drugs (NSAIDs) or colchicine to treat the flare-up and prevent more flares. You may need to take these drugs for up to 6 months. Symptoms of gout include pain, swelling, redness, heat, soreness, and stiffness in your big toe or other joints.

allergies
Allergies

Allopurinol can cause a severe allergic reaction. Symptoms can include:

  • itchy hives (raised bumps on your skin)
  • red or purple-colored spots on your skin
  • scaly skin
  • fever
  • chills
  • trouble breathing
  • swelling of your face or throat 

If you have an allergic reaction, call your doctor or local poison control center right away. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

SECTION 4 of 5

How to Take allopurinol (Dosage)

Oral tablet

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Gout

Generic: allopurinol

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Xyloprim

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Lopurin

Form: Oral tablet
Strengths: 100 mg, 300 mg
Adult dosage (ages 18–64 years)
  • Typical starting dose: 100 mg per day
  • Dose adjustments: Your doctor may increase your dose by 100 mg per week until you’ve reached the desired level of serum uric acid.
  •  Usual dose:
    • Mild gout: 200–300 mg per day
    • Moderate to severe gout: 400–600 mg per day
  • Maximum dose: 800 mg per day taken in divided doses
Child dosage (ages 0–17 years)

This medication hasn’t been studied and shouldn’t be used in people younger than 18 years for this condition.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Special considerations

Kidney disease: Depending on how well your kidneys are working, your doctor will lower your dose. Your doctor will decide your dosage based on your creatinine clearance. This is a test that measures your kidney function.

Creatinine clearance of:

  • 10–20 mL/min: 200 mg per day
  • less than 10 mL/min: Your total dose per day shouldn’t be higher than100 mg.
  • less than 3 mL/min: The time between doses may also need to be increased. You may only take this drug once every other day.

Elevated serum uric acid levels due to cancer treatments

Generic: allopurinol

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Xyloprim

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Lopurin

Form: Oral tablet
Strengths: 100 mg, 300 mg
Adult dosage (ages 18–64 years)
  • Typical starting dose: 100 mg per day
  • Dose adjustments: Your doctor may increase your dose by 100 mg per week until you’ve reached the desired level of serum uric acid.
  •  Usual dose:
    • Mild gout: 200–300 mg per day
    • Moderate to severe gout: 400–600 mg per day
  • Maximum dose: 800 mg per day taken in divided doses
Child dosage (ages 11–17 years)

To prevent uric acid problems in the kidneys of people with cancer on chemotherapy:

  • 600–800 mg per day for 2 or 3 days
Child dosage (ages 6–10 years)

To prevent uric acid problems in the kidneys of people with cancer on chemotherapy:

  • 300 mg per day. Your doctor will adjust your dose as needed based on your serum uric acid level.
Child dosage (ages 0–5 years)

To prevent uric acid problems in the kidneys of people with cancer on chemotherapy:

  • 150 mg per day. Your doctor will adjust your dose as needed based on your serum uric acid level.
Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Special considerations

Kidney disease: Depending on how well your kidneys are working, your doctor will lower your dose. Your doctor will decide your dosage based on your creatinine clearance. This is a test that measures your kidney function.

Creatinine clearance of:

  • 10–20 mL/min: 200 mg per day
  • less than 10 mL/min: Your total dose per day shouldn’t be higher than100 mg.
  • less than 3 mL/min: The time between doses may also need to be increased. You may only take this drug once every other day.

Recurrent kidney stones

Generic: allopurinol

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Xyloprim

Form: Oral tablet
Strengths: 100 mg, 300 mg

Brand: Lopurin

Form: Oral tablet
Strengths: 100 mg, 300 mg
Adult dosage (ages 18–64 years)

Usual dose: 200–300 mg per day taken in a single or divided doses.

Child dosage (ages 0–17 years)

This medication hasn’t been studied and shouldn’t be used in people younger than 18 years for this condition.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Special considerations

Kidney disease: Depending on how well your kidneys are working, your doctor will lower your dose. Your doctor will decide your dosage based on your creatinine clearance. This is a test that measures your kidney function.

Creatinine clearance of:

  • 10–20 mL/min: 200 mg per day
  • less than 10 mL/min: Your total dose per day shouldn’t be higher than100 mg.
  • less than 3 mL/min: The time between doses may also need to be increased. You may only take this drug once every other day.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Allopurinol comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all

Your blood and/or urine uric acid levels will stay high. If you have gout or kidney stones, you’ll still have symptoms of your condition.

If you miss doses or don’t take the drug on schedule

Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much

You could have dangerous levels of the drug in your body.  Symptoms can include:

  • skin rash
  • diarrhea
  • nausea
  • changes in your liver function test results
  • gout flare-up (if you have gout)

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room right away.

What to do if you miss a dose

Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working

Your doctor will test your uric acid levels to check if this drug is working. Your blood uric acid levels will decrease about 1–3 weeks after you start taking this drug. Your doctor will also ask you about how much fluids you drink and how much fluids you urinate.

Right after you start taking this drug, you may have gout flares. Over time, your symptoms of gout may start to go away.

Allopurinol is used for long-term treatment.

Important considerations for taking this drug
You can take with or without food
You can take allopurinol with or without food
See Details
timing
Take this drug at the time(s) recommended by your doctor
can crush or cut
You can cut or crush the tablet
storage
Store this drug carefully
See Details
refillable
A prescription for this medication is refillable
See Details
travel
Travel
See Details
clinical monitoring
Clinical monitoring
See Details
your diet
Your diet
See Details
not usually stocked
Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead

You can take allopurinol with or without food

Taking it after a meal and with lots of water may reduce your chance of upset stomach.

Store this drug carefully

  • Store allopurinol at room temperature. Keep it between 68°F and 77°F (20°C and 25°C).
  • Keep it away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

A prescription for this medication is refillable

You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

You and your doctor should monitor certain health issues. This can help make sure you stay safe while you take this drug. These issues include:

  • Kidney function. Your doctor may do blood tests to check how well your kidneys are working. If your kidneys aren’t working well, your doctor may lower your dose of this drug.
  • Liver function. Your doctor may do blood tests to check how well your liver is working. If your liver isn’t working well, your doctor may lower your dose of this drug.
  • Uric acid levels. Your doctor may do blood tests to check your uric acid. This will help your doctor tell how well this drug is working.

Your diet

If you have repeat kidney stones, your doctor may tell you to eat a special diet. This diet is low in animal protein (meat), sodium, sugar, and oxalate-rich foods (such as, spinach, beets, celery, and green beans). Your diet should also be high in fiber. You should drink plenty of water. You may also need to watch your calcium intake.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

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How Much Does allopurinol Cost?

Oral tablet

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Lowest price for allopurinol

Walmart $4.00
Sams Club $6.45
Kroger Pharmacy $7.75
These prices represent the lowest priced national pharmacies for allopurinol on GoodRx. They may be lower than your insurance.

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These prices represent the lowest priced national pharmacies for allopurinol on GoodRx. They may be lower than your insurance.

Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on November 12, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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