Side Effects

Drug information provided by: Micromedex

Along with their needed effects, medicines like thioguanine can sometimes cause unwanted effects such as blood problems and other side effects. These and others are described below. Also, because of the way these medicines act on the body, there is a chance that they might cause other unwanted effects that may not occur until months or years after the medicine is used. These delayed effects may include certain types of cancer, such as leukemia. Discuss these possible effects with your doctor.

Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

  1. Black, tarry stools
  2. blood in urine or stools
  3. cough or hoarseness
  4. fever or chills
  5. lower back or side pain
  6. painful or difficult urination
  7. pinpoint red spots on skin
  8. unusual bleeding or bruising

Check with your doctor as soon as possible if any of the following side effects occur:

Less common

  1. Joint pain
  2. swelling of feet or lower legs
  3. unsteadiness when walking


  1. Sores in mouth and on lips
  2. yellow eyes or skin

Frequency not determined

  1. Abdominal or stomach pain
  2. bloated abdomen
  3. chest pain or discomfort
  4. cough or hoarseness
  5. coughing up blood
  6. dark urine
  7. dizziness
  8. fainting
  9. fatigue
  10. headache
  11. hives
  12. itching
  13. light-colored stools
  14. loss of appetite
  15. lower back or side pain
  16. nausea
  17. pain and fullness in right upper abdomen
  18. pale skin
  19. purple- or red-colored spots on body or inside the mouth or nose
  20. rash
  21. shortness of breath
  22. sore throat
  23. swollen glands
  24. unpleasant breath odor
  25. unusual tiredness or weakness
  26. vomiting
  27. vomiting of blood
  28. weight gain

Some 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. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

  1. Diarrhea
  2. loss of appetite
  3. nausea and vomiting
  4. skin rash or itching

After you stop using this medicine, it may still produce some side effects that need attention. During this period of time, check with your doctor immediately if you notice the following side effects:

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

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.