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Thioguanine Side Effects

For the Consumer

Applies to thioguanine: oral tablet

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 while taking thioguanine:

More Common

  • Black, tarry stools
  • blood in urine or stools
  • cough or hoarseness
  • fever or chills
  • lower back or side pain
  • painful or difficult urination
  • pinpoint red spots on skin
  • unusual bleeding or bruising

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

Less Common

  • Joint pain
  • swelling of feet or lower legs
  • unsteadiness when walking


  • Sores in mouth and on lips
  • yellow eyes or skin

Frequency not determined

  • Abdominal or stomach pain
  • bloated abdomen
  • chest pain or discomfort
  • cough or hoarseness
  • coughing up blood
  • dark urine
  • dizziness
  • fainting
  • fatigue
  • headache
  • hives
  • itching
  • light-colored stools
  • loss of appetite
  • lower back or side pain
  • nausea
  • pain and fullness in right upper abdomen
  • pale skin
  • purple- or red-colored spots on body or inside the mouth or nose
  • rash
  • shortness of breath
  • sore throat
  • swollen glands
  • unpleasant breath odor
  • unusual tiredness or weakness
  • vomiting
  • vomiting of blood
  • weight gain

Some side effects of thioguanine 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

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:

  • Black, tarry stools
  • blood in urine or stools
  • cough or hoarseness
  • fever or chills
  • lower back or side pain
  • painful or difficult urination
  • pinpoint red spots on skin
  • unusual bleeding or bruising

For Healthcare Professionals

Applies to thioguanine: oral tablet


Because thioguanine may have delayed effect, the drug should be withdrawn temporarily at the first sign of an abnormally large fall in any of the formed elements of the blood.

Hyperuricemia can be minimized by increased hydration, urine alkalinization, and the prophylactic administration of a xanthine oxidase inhibitor such as allopurinol.[Ref]

Hematologic side effects including myelosuppression have been reported. Myelosuppression is the most frequent adverse reaction to thioguanine and may appear as anemia, leukopenia, and/or thrombocytopenia. The induction of complete remission of acute myelogenous leukemia usually requires combination chemotherapy in dosages which produce marrow hypoplasia. Since consolidation and maintenance of remission are also affected by multiple drug regimens whose component agents cause myelosuppression, pancytopenia is observed in nearly all patients.

Hyperuricemia frequently occurs in patients receiving thioguanine as a consequence of rapid cell lysis accompanying the antineoplastic effect.

Life-threatening infection and bleeding have been observed as consequences of thioguanine-induced granulocytopenia and thrombocytopenia.[Ref]


Gastrointestinal side effects including nausea, vomiting, diarrhea, anorexia, and stomatitis have been reported. Intestinal necrosis and perforation have been reported in patients who received multiple drug chemotherapy which included thioguanine.[Ref]

If severe diarrhea and/or stomatitis develop, a decrease in dosage may be appropriate.[Ref]


Hepatic side effects including veno-occlusive liver disease have been reported. A case of peliosis hepatitis has been reported. Liver enzyme and other liver function studies are occasionally abnormal.[Ref]

If jaundice, hepatomegaly, or anorexia with tenderness in the right hypochondrium occurs, thioguanine should be withheld until the exact etiology can be determined.[Ref]


Respiratory side effects including esophageal varices have been reported in patients receiving continuous busulfan and thioguanine therapy. Nasal congestion and rhinorrhea have been reported with high dose IV therapy.[Ref]


Renal side effects including nephrotoxicity have been reported in high-dose therapy.[Ref]


Dermatologic side effects including the development of painful erythematous swelling of the palms and soles occurring several days after courses of therapy, have been reported in 5 women on cytarabine, doxorubicin, and thioguanine. Alopecia has also been reported.[Ref]


Other side effects including malaise, lethargy, weakness, ataxia, and loss of vibratory sensation have been reported.[Ref]


Cardiovascular side effects have been reported. In one study, two of thirteen patients administered 700 mg/m2 intravenously developed bradycardia and nonspecific T-wave flattening, which resolved within 3 hours. In another study, five of nineteen patients administered 1000 mg/m2 intravenously demonstrated minor changes: bradycardia (two patients), nonspecific ST- and T-wave changes (five), and P-wave changes (one).[Ref]


1. Ajani JA, Pazdur R, Winn RJ, Abbruzzese JL, Levin B, Wiseman C, Lenado-Lee MA, Patt YZ, Krakoff IH "Phase II study of intravenous 6-thioguanine in patients with advanced gastric carcinoma." Invest New Drugs 9 (1991): 257-9

2. "Product Information. Tabloid (thioguanine)." Glaxo Wellcome, Research Triangle Park, NC.

3. Presant CA, Denes AE, Klein L, Garrett S, Metter GE "Phase I and preliminary phase II observations of high-dose intermittent 6-thioguanine." Cancer Treat Rep 64 (1980): 1109-13

4. Shevrin DH, Kilton LJ, Lad TE, Mullane M, Esparaz B, Knop R, Egner J, Johnson P, Blough R, French S, et al "Phase II trial of 6-thioguanine in advanced renal cell carcinoma. An Illinois Cancer Center study." Invest New Drugs 12 (1994): 345-6

5. Britell JC, Moertel CG, Kvols LK, O'Connell MJ, Rubin J, Schutt AJ "Phase II trial of iv 6-thioguanine in advanced colorectal carcinoma." Cancer Treat Rep 65 (1981): 909-10

6. Ajani JA, Pazdur R, Winn RJ, Abbruzzese JL, Levin B, Belt R, Young J, Patt YZ, Krakoff IH "Phase II study of intravenous 6-thioguanine in patients with advanced carcinoma of the pancreas." Invest New Drugs 9 (1991): 369-71

7. Williamson SK, Crowley J, Livingston RB, Weiss G "Phase II trial of 6-thioguanine administered as 120 hour continuous infusion for refractory or recurrent small cell lung cancer. A Southwest Oncology Group study." Invest New Drugs 11 (1993): 81-3

8. Griner PF, Elbadawi A, Packman CH "Veno-occlusive disease of the liver after chemotherapy of acute leukemia. Report of two cases." Ann Intern Med 85 (1976): 578-82

9. Larrey D, Freneaux E, Berson A, Babany G, Degott C, Valla D, Pessayre D, Benhamou JP "Peliosis hepatis induced by 6-thioguanine administration." Gut 29 (1988): 1265-9

10. Satti MB, Weinbren K, Gordon-Smith EC "6-thioguanine as a cause of toxic veno-occlusive disease of the liver." J Clin Pathol 35 (1982): 1086-91

11. Kao NL, Rosenblate HJ "6-Thioguanine therapy for psoriasis causing toxic hepatic venoocclusive disease." J Am Acad Dermatol 28 (1993): 1017-8

12. Gill RA, Onstad GR, Cardamone JM, Maneval DC, Sumner HW "Hepatic veno-occlusive disease caused by 6-thioguanine." Ann Intern Med 96 (1982): 58-60

13. Weiss RB, Poster DS "The renal toxicity of cancer chemotherapeutic agents." Cancer Treat Rev 9 (1982): 37-56

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.