Allopurinol is used to prevent or treat high uric acid levels in the blood. Gout or gouty arthritis (inflammation and pain in a joint) is caused by high uric acid levels. Allopurinol is a xanthine oxidase inhibitor that works by causing less uric acid to be produced by the body.

Allopurinol is also used to prevent or treat high uric acid levels that may be caused by cancer medicines or for patients with kidney stones that contain calcium.

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

Take this medication by mouth, usually once daily or as directed by your doctor. Take this medication after a meal to reduce stomach upset. If your dose is more than 300 milligrams a day, you will need to take several smaller doses during the day to get this amount (ask your doctor for directions).

It is best to drink a full glass of water with each dose and at least 8 more glasses (8 ounces each) of fluid a day. If your doctor has directed you to drink less fluid for other medical reasons, consult your doctor for further instructions. Your doctor may also instruct you on how to decrease acid in your urine (e.g., avoiding large amounts of ascorbic acid/vitamin C).

Dosage is based on your medical condition and response to treatment. Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time(s) each day.

For the treatment of gout, it may take up to several weeks for this medicine to have an effect. You may have more gout attacks for several months after starting this medicine while the body removes extra uric acid. Allopurinol is not a pain reliever. To relieve pain from gout, continue to take your prescribed medicines for gout attacks (e.g., colchicine, ibuprofen, indomethacin) as directed by your doctor.

Tell your doctor if your condition persists or worsens.

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.

Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.

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.

Stomach upset, nausea, diarrhea, or drowsiness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if any of these rare but very serious side effects occur: numbness/tingling of arms/legs, easy bleeding/bruising, unusual tiredness, signs of kidney problems (such as change in the amount of urine, painful/bloody urination), yellowing eyes/skin, severe stomach/abdominal pain, persistent nausea/vomiting, dark urine, unusual weight loss, eye pain, vision changes.

This medication can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Get medical help right away if you develop any rash.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever, swollen lymph nodes, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. If this medicine upsets your stomach, take it with food or milk. Take your doses at regular intervals. Do not take your medicine more often than directed.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed. While this drug may be prescribed for children as young as 6 years for selected conditions, precautions do apply.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What should I watch for while using this medicine?

Visit your doctor or health care professional for regular checks on your progress. If you are taking this medicine to treat gout, you may not have less frequent attacks at first. Keep taking your medicine regularly and the attacks should get better within 2 to 6 weeks. Drink plenty of water (10 to 12 full glasses a day) while you are taking this medicine. This will help to reduce stomach upset and reduce the risk of getting gout or kidney stones.

Call your doctor or health care professional at once if you get a skin rash together with chills, fever, sore throat, or nausea and vomiting, if you have blood in your urine, or difficulty passing urine.

Do not take vitamin C without asking your doctor or health care professional. Too much vitamin C can increase the chance of getting kidney stones.

You may get drowsy or dizzy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this drug affects you. Do not stand or sit up quickly, especially if you are an older patient. This reduces the risk of dizzy or fainting spells. Alcohol can make you more drowsy and dizzy. Alcohol can also increase the chance of stomach problems and increase the amount of uric acid in your blood. Avoid alcoholic drinks.