What side effects may I notice from receiving Mercaptopurine?

Side effects that you should report to your doctor or health care professional as soon as possible:

-allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
-breathing problems
-low blood counts - this medicine may decrease the number of white blood cells, red blood cells and platelets. You may be at increased risk for infections and bleeding
-signs of decreased platelets or bleeding - bruising, pinpoint red spots on the skin, black, tarry stools, blood in the urine
-signs of decreased red blood cells - unusually weak or tired, feeling faint or lightheaded, falls
-signs of infection - fever or chills, cough, sore throat, pain or difficulty passing urine
-signs and symptoms of liver injury like dark yellow or brown urine; general ill feeling or flu-like symptoms; light-colored stools; loss of appetite; nausea; right upper belly pain; unusually weak or tired; yellowing of the eyes or skin
-sore throat
-swelling of the stomach

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):

-diarrhea
-hair loss
-mouth sores
-vomiting

This list may not describe all possible side effects for Mercaptopurine. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.