What side effects can this medication cause?

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

Allopurinol may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online at http://www.fda.gov/MedWatch/report.htm or by phone 1-800-332-1088.