Leukemia Home > Purinethol Warnings and Precautions

Discuss your medical history with your healthcare provider before starting treatment with Purinethol. Although this can be an effective form of chemotherapy, Purinethol may not be the best option for people who have liver disease, inflammatory bowel disease, or kidney disease. Safety precautions with Purinethol also include warnings of serious drug interactions, allergic reactions, and dangerously low blood cell counts.

What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to taking Purinethol® (mercaptopurine) if you have:
  • Liver disease, such as hepatitis, cirrhosis, or liver failure
  • Kidney disease, such as kidney failure (renal failure)
  • Been previously treated with Purinethol or a medicine known as thioguanine (Tabloid®)
  • Been told you have thiopurine-S-methyltransferase (TPMT) deficiency or a defect in the TPMT gene
  • Inflammatory bowel disease, such as Crohn's disease or ulcerative colitis
  • Plans to receive a vaccination
  • Any allergies, including allergies to foods, dyes, or preservatives.
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
You should also tell your healthcare provider about all other medications you are taking, including prescription and nonprescription medicines, vitamins, and herbal supplements.

Specific Precautions and Warnings for Purinethol

Some warnings and precautions to be aware of prior to taking this medication include the following:
  • Purinethol is a potent anticancer medication associated with potentially serious side effects. It should only be prescribed by a healthcare provider with experience using this drug and assessing response to chemotherapy.
  • You will need regular blood tests during treatment to make sure the medication is working, and to check for potentially serious side effects. Your healthcare provider may need to adjust your dose frequently based on your response to treatment.
  • This medication may increase the risk for developing cancer. There have been reports of a rare but serious cancer known as hepatosplenic lymphoma T-cell lymphoma occurring in people being treated with Purinethol for inflammatory bowel disease (such as Crohn's disease or ulcerative colitis). At this time, it is unknown whether Purinethol is safe or effective for people with inflammatory bowel disease.
  • Purinethol can cause bone marrow suppression (when the bone marrow is unable to produce adequate amounts of blood cells), which can lead to abnormally low white blood cells, red blood cells, and platelets. As a result, you will have an increased risk for potentially serious infections, anemia, and bleeding problems. Let your healthcare provider know if you have signs of bone marrow suppression, such as:
    • Signs of low platelets, such as:
      • Any abnormal bleeding or bruising
      • Blood in your urine or stools
      • Black, tarry stools
      • Small red or purple spots under the skin
    • Signs of anemia, such as:
      • Fatigue
      • Weakness
      • Shortness of breath
      • Pale skin
    • Signs of infection, such as:
      • Fever
      • Chills
      • Sore throat
      • Cough or shortness of breath
      • Burning or pain when urinating.
  • Some people have an inherited defect in a certain gene known as the thiopurine-S-methyltransferase (TPMT) gene. This defect causes low activity of an enzyme in the body known as TPMT. People with low TPMT activity are more likely to develop rapid bone marrow suppression when starting Purinethol treatment, and may need lower-than-normal Purinethol doses. Your healthcare provider can test you for this gene, or check your TPMT activity with a blood test, and reduce your Purinethol dose if necessary. 
  • This medication may cause liver damage, especially in doses higher than the usual recommended dose. Your healthcare provider will perform blood tests to monitor your liver function throughout treatment. Let him or her know if you have any signs of liver problems, such as:
    • Yellowing of the skin or whites of the eyes
    • Upper-right abdominal (stomach) pain
    • Loss of appetite.
  • Purinethol is eliminated from the body by the kidneys. Therefore, people who have kidney disease may eliminate the drug more slowly and may need lower doses.  
  • Cancer that is resistant to a medication known as thioguanine is also usually resistant to Purinethol. Make sure your healthcare provider knows if you have been treated with thioguanine.
  • Purinethol is a pregnancy Category D medication, which means it may harm an unborn child. Talk to your healthcare provider about the risks and benefits of using this medication during pregnancy (see Purinethol and Pregnancy).
  • It is unknown if Purinethol passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking Purinethol (see Purinethol and Breastfeeding).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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