Medical Editor: John P. Cunha, DO, FACOEP Last updated on RxList: 4/26/2022
Purinethol Side Effects Center

What Is Purinethol?

Purinethol (mercaptopurine) is a cancer medication that interferes with the growth of cancer cells and slows their growth and spread in the body used to treat acute lymphatic leukemia or acute myelogenous leukemia. Purinethol is usually given together with other cancer medications. Purinethol is available in generic form.

What Are Side Effects of Purinethol?

Common side effects of Purinethol include:

Temporary hair loss may also occur. Normal hair growth should return after treatment with Purinethol has ended. Tell your doctor if you have unlikely but serious side effects of Purinethol including:

Dosage for Purinethol

The usual daily maintenance dose of Purinethol is 1.5 to 2.5 mg/kg/day as a single dose.

What Drugs, Substances, or Supplements Interact with Purinethol?

Purinethol may interact with allopurinol, azathioprine, blood thinners, cyclosporine, olsalazine or sulfasalazine, sulfamethoxasole and trimethoprim, or thioguanine. Tell your doctor all medications you are taking.

Purinethol During Pregnancy and Breastfeeding

Purinethol is not recommended for use during pregnancy. It may harm the fetus, particularly during the first 3 months of pregnancy. It is not known whether this drug passes into breast milk. Because of the possible risk to the infant, breastfeeding while using this drug is not recommended.

Additional Information

Our Purinethol (mercaptopurine) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Purinethol Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • low blood cell counts--fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath;
  • liver problems--loss of appetite, nausea, vomiting, diarrhea, upper stomach pain, swelling in your midsection, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • symptoms of lymphoma--fever, night sweats, tiredness, stomach bloating, feeling full, weight loss.

Common side effects may include:

  • low blood cell counts;
  • bruising or bleeding;
  • nausea, vomiting, loss of appetite;
  • diarrhea;
  • rash, changes in skin color;
  • hair loss; or
  • general ill feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Purinethol (Mercaptopurine)


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Purinethol Professional Information


The following clinically significant adverse reactions are described elsewhere in the labeling:

  • Myelosuppression [see WARNINGS AND PRECAUTIONS]
  • Hepatotoxicity [see WARNINGS AND PRECAUTIONS]
  • Immunosuppression [see WARNINGS AND PRECAUTIONS]
  • Treatment related malignancies [see WARNINGS AND PRECAUTIONS]
  • Macrophage activation syndrome [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Based on multicenter cooperative group ALL trials, the most common adverse reaction occurring in > 20% of patients was myelosuppression, including anemia, neutropenia, lymphopenia and thrombocytopenia. Adverse reactions occurring in 5% to 20% of patients included anorexia, nausea, vomiting, diarrhea, malaise and rash. Adverse reactions occurring in < 5 % of patients included urticaria, hyperuricemia, oral lesions, increased transaminases, hyperbilirubinemia, hyperpigmentation, infections, and pancreatitis. Oral lesions resemble thrush rather than antifolic ulcerations. Delayed or late adverse reactions include hepatic fibrosis, hyperbilirubinemia, alopecia, pulmonary fibrosis, oligospermia and secondary malignancies [see WARNINGS AND PRECAUTIONS].

Drug fever has been reported with mercaptopurine.

Additional adverse reactions that have been reported in patients who have received mercaptopurine include photosensitivity, hypoglycemia, and portal hypertension.

Read the entire FDA prescribing information for Purinethol (Mercaptopurine)

© Purinethol Patient Information is supplied by Cerner Multum, Inc. and Purinethol Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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