Allopurinol is in a class of medications called xanthine oxidase inhibitors. It works by reducing the production of uric acid in the body. High levels of uric acid may cause gout attacks or kidney stones. Allopurinol is used to prevent gout attacks, not to treat them once they occur.

Allopurinol is also sometimes used to treat seizures, pain caused by pancreas disease, and certain infections. It is also sometimes used to improve survival after bypass surgery, to reduce ulcer relapses, and to prevent rejection of kidney transplants. Talk to your doctor about the possible risks of using this medicine for your condition.

Special precautions

Before taking allopurinol,

• Tell your doctor and pharmacist if you are allergic to allopurinol or any other medicines.
• Tell your doctor if you have or have ever had kidney or liver disease or heart failure.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking allopurinol, call your doctor.
• You should know that allopurinol may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
• Ask your doctor about the safe use of alcoholic beverages while you are taking allopurinol. Alcohol may decrease the effectiveness of allopurinol.

Side effects

Allopurinol may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• upset stomach
• diarrhea
• drowsiness

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, call your doctor immediately:

• skin rash
• painful urination
• blood in the urine
• irritation of the eyes
• swelling of the lips or mouth
• fever, sore throat, chills, and other signs of infection
• loss of appetite
• unexpected weight loss
• itching

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to allopurinol.