Description and Brand Names

Drug information provided by: Merative, Micromedex®

US Brand Name

  1. Zyloprim


Allopurinol is used to prevent or lower high uric acid levels in the blood. It is also used to prevent or lower excess uric acid levels caused by cancer medicines or in patients with kidney stones. A high uric acid level can cause gout or gouty arthritis (joint pain and inflammation). Allopurinol is a xanthine oxidase inhibitor that works by decreasing the uric acid produced by the body.

This medicine is available only with your doctor's prescription.

This product is available in the following dosage forms:

  • Tablet

Before Using

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of allopurinol in children with high uric acid levels caused by cancer.


No information is available on the relationship of age to the effects of allopurinol in geriatric patients.


There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Didanosine

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acenocoumarol
  • Azathioprine
  • Capecitabine
  • Captopril
  • Enalapril
  • Enalaprilat
  • Fluorouracil
  • Levoketoconazole
  • Mercaptopurine
  • Methotrexate
  • Pegloticase
  • Phenprocoumon
  • Tegafur
  • Warfarin

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Aluminum Hydroxide
  • Cyclosporine
  • Vidarabine

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Bone marrow problems or
  • Liver disease—Use with caution. May make these conditions worse.
  • Cancer (eg, multiple myeloma) or
  • Congestive heart disease or
  • Diabetes or
  • Hypertension (high blood pressure) or
  • Hyperuricemia (high uric acid level in the blood) or
  • Kidney problems, chronic (eg, glomerulonephritis, pyelonephritis)—Use with caution. May cause side effects to become worse.
  • Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

Proper Use

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.

You may take this medicine after meals to avoid stomach upset.

Take this medicine with plenty of liquids to help prevent kidney stones. Check with your doctor about the amount of liquid you should drink each day. You should also increase your fiber intake.

You may need to lessen your intake of animal protein, sodium, refined sugars, or foods rich in oxalate and calcium, especially if you have kidney stones that keep coming back.


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—300 to 800 milligrams (mg) per day. Your doctor may adjust your dose as needed.
      • Children—Dose is based on body surface area (BSA) and must be determined by your doctor. The dose is usually 100 milligrams per square meter (mg/m[2]) every 8 to 12 hours. Your doctor may adjust your dose as needed. However, the dose is usually not more than 800 mg per day.
    • 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.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.


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.

Serious skin reactions can occur with this medicine, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS). Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness.

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.

This medicine may cause serious kidney problem. Check with your doctor right away if you have blood in the urine, change in frequency of urination or amount of urine, difficulty in breathing, drowsiness, increased thirst, loss of appetite, nausea or vomiting, swelling of the feet or lower legs, or weakness.

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 lowers the number of some types of blood cells in your body. Because of this, you may bleed or get infections more easily. To help with these problems, avoid being near people who are sick or have infections. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.

This medicine may cause some people to become drowsy, dizzy, 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.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

  1. Ankle, knee, or great toe joint pain
  2. joint stiffness or swelling
  3. rash
  4. rash with flat lesions or small raised lesions on the skin


  1. Agitation
  2. ammonia-like breath odor
  3. anxiety
  4. bleeding gums
  5. blistering, peeling, or loosening of the skin
  6. blood in the urine or stools
  7. bloody nose
  8. bloody or black, tarry stools
  9. blue or pale skin
  10. bruising
  11. changes in skin color
  12. chest pain, tightness, or discomfort
  13. chest pain, possibly moving to the left arm, neck, or shoulder
  14. chills
  15. clay-colored stools
  16. cloudy urine
  17. confusion
  18. constipation
  19. cough
  20. coughing up blood
  21. cracks in the skin
  22. dark urine
  23. decreased awareness or responsiveness
  24. decreased urine output
  25. depression
  26. diarrhea
  27. difficulty with breathing
  28. dizziness
  29. drowsiness
  30. dry mouth
  31. feeling of warmth or heat
  32. fever
  33. flushing or redness of the skin, especially on the face and neck
  34. general feeling of discomfort or illness
  35. headache
  36. hives or welts, itching, skin rash
  37. hoarseness
  38. hostility
  39. incoherent speech
  40. increased urination
  41. irritability
  42. joint or muscle pain
  43. large, flat, blue or purplish patches in the skin
  44. light-colored stools
  45. loss of appetite
  46. loss of consciousness
  47. loss of heat from the body
  48. lower back or side pain
  49. metallic taste
  50. muscle twitching or weakness
  51. nausea
  52. noisy breathing
  53. pain, tenderness, or swelling of the foot or leg
  54. painful or difficult urination
  55. pinpoint red or purple spots on the skin
  56. rapid weight gain
  57. red, irritated eyes
  58. red, swollen skin
  59. redness, soreness, or itching skin
  60. right upper abdominal or stomach pain and fullness
  61. scaly skin
  62. seizures
  63. severe sleepiness
  64. severe stomach pain
  65. slow or irregular heartbeat
  66. sore throat
  67. sores, ulcers, or white spots on the lips or in the mouth
  68. sores, welting, or blisters
  69. stomach pain
  70. sweating
  71. swelling of the face, ankles, hands, or lower legs
  72. swollen or painful glands
  73. swollen, painful, or tender lymph glands in the neck, armpit, or groin
  74. thirst
  75. unpleasant breath odor
  76. unusual bleeding or bruising
  77. unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  78. unusual weight gain or loss
  79. vomiting
  80. vomiting of blood or material that looks like coffee grounds
  81. yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:


  1. Bad, unusual, or unpleasant (after) taste
  2. blindness
  3. blue-yellow color blindness
  4. blurred vision
  5. body aches or pain
  6. burning feeling in the chest or stomach
  7. burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  8. burning, dry, or itching eyes
  9. change in taste
  10. change in vision
  11. congestion
  12. continuing ringing or buzzing or other unexplained noise in the ears
  13. decreased interest in sexual intercourse
  14. decreased vision
  15. difficulty with moving
  16. discharge or excessive tearing
  17. feeling of constant movement of self or surroundings
  18. hair loss or thinning of the hair
  19. hearing loss
  20. impaired vision
  21. inability to have or keep an erection
  22. indigestion
  23. lack or loss of strength
  24. loss in sexual ability, desire, drive, or performance
  25. loss of appetite
  26. loss of memory
  27. multiple swollen and inflamed skin lesions
  28. muscle pain, cramps, stiffness, tenderness, or wasting
  29. problems with memory
  30. redness, pain, or swelling of the eye, eyelid, or inner lining of the eyelid
  31. runny nose
  32. sensation of spinning
  33. sensitivity to light
  34. sleepiness or unusual drowsiness
  35. sleeplessness
  36. sneezing
  37. stomach upset
  38. stuffy nose
  39. sweating
  40. swelling of the breasts or breast soreness in both females and males
  41. swelling of the salivary glands
  42. swelling or inflammation of the mouth
  43. tearing
  44. tender, swollen glands in the neck
  45. tenderness in the stomach area
  46. throbbing pain
  47. trouble getting pregnant
  48. trouble with sleeping
  49. trouble with swallowing
  50. unsteadiness or awkwardness
  51. voice changes
  52. weakness in the arms, hands, legs, or feet
  53. weight loss

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.