Your doctor should check your progress at regular visits. Blood tests may be needed to make sure that ALLOPURINOL is working properly and is not causing unwanted effects.

Drinking too much alcohol may increase the amount of uric acid in the blood and lessen the effects of allopurinol. Therefore, people with gout and other people with too much uric acid in the body should be careful to limit the amount of alcohol they drink.

Taking too much vitamin C may make the urine more acidic and increase the possibility of kidney stones forming while you are taking allopurinol. Therefore, check with your doctor before you take vitamin C while taking ALLOPURINOL.

Check with your doctor immediately:

• If you notice a skin rash, hives, or itching while you are taking allopurinol.
• If chills, fever, joint pain, muscle aches or pains, sore throat, or nausea or vomiting occur, especially if they occur together with or shortly after a skin rash.

Very rarely, these effects may be the first signs of a serious reaction to the medicine.

Allopurinol may cause some people to become drowsy or less alert than they are normally. Make sure you know how you react to ALLOPURINOL before you drive, use machines, or do anything else that could be dangerous if you are not alert.

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.

Stop taking ALLOPURINOL and check with your doctor immediately if any of the following side effects occur:

• More common
  • Skin rash or sores, hives, or itching 
  
  

• Rare
  • Black, tarry stools;  bleeding sores on lips;  blood in urine or stools;  chills, fever, muscle aches or pains, nausea, or vomiting—especially if occurring with or shortly after a skin rash;  difficult or painful urination;  pinpoint red spots on skin;  redness, tenderness, burning, or peeling of skin;  red and/or irritated eyes;  red, thickened, or scaly skin;  shortness of breath, troubled breathing, tightness in chest, or wheezing;  sores, ulcers, or white spots in mouth or on lips;  sore throat and fever;  sudden decrease in amount of urine;  swelling in upper abdominal (stomach) area;  swelling of face, fingers, feet, or lower legs ;  swollen and/or painful glands;  unusual bleeding or bruising;  unusual tiredness or weakness;  weight gain (rapid);  yellow eyes or skin 
  
  

Also, check with your doctor as soon as possible if any of the following side effects occur:

• Rare
  • Loosening of fingernails;  numbness, tingling, pain, or weakness in hands or feet;  pain in lower back or side;  unexplained nosebleeds 
  
  

Other 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. However, check with your doctor if any of the following side effects continue or are bothersome:

• Less common or rare
  • Diarrhea;  drowsiness;  headache;  indigestion;  nausea or vomiting occurring without a skin rash or other side effects;  stomach pain occurring without other side effects;  unusual hair loss 
  
  

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