Mercaptopurine is an anticancer drug that belongs to the class of medicines known as purine antagonists. It was approved by the U.S. FDA on 28th of April 2014 to treat acute lymphoblastic leukaemia.

Mercaptopurine is used in the treatment of acute lymphoblastic leukaemia.

Mercaptopurine is to be administered orally. Swallow the whole tablet with water. If you forgot to take the tablet, simply take your next dose at the scheduled time. Do not take a double dose to make up for a forgotten dose. You must take these tablets at least 1 hour before or 2 hours after having milk or dairy products.

The common side effects that are likely to occur while you are on the treatment with mercaptopurine are nausea, vomiting, anaemia, fever or infection (sore throat, sore mouth, or urinary problems), unexplained bruising or bleeding, low white blood cell and platelet count. If you experience any allergic or unusual reactions after taking this medicine, report to your doctor immediately.

If you are going to have a vaccination, speak to your doctor or nurse before you have it. When you take this drug, you should not have a live vaccine (like polio, measles, mumps and rubella.) until advised it is safe to do so by your doctor. This is because some vaccines may give you an infection if you have them while you are taking this drug. Do not get vaccinated with yellow fever vaccine while you are taking this drug because it may lead to serious illness. Your doctor may also ask for other blood and urine tests to monitor how your kidneys are working and to measure uric acid levels. Uric acid is a natural substance made in your body and levels of uric acid can rise while you are taking this drug. High levels of uric acid may damage your kidneys, so your doctor may sometimes change your dose of the drug as a result of these tests. It is probably advisable to start with lower doses in patients with impaired renal function, due to slower elimination of the drug and metabolites and a greater cumulative effect. Consideration should be given to reducing the dosage in patients with impaired hepatic function.

This drug is not recommended during pregnancy as it causes harm to the unborn baby. Tell your healthcare provider before beginning this treatment if you are pregnant or planning to have a baby. It is advised for both men and women to follow proper contraceptive methods during and for 3 months after the last dose of Mercaptopurine. During the treatment, your doctor may periodically monitor your white blood cell counts, platelets, blood sugar, electrolytes and kidney parameters to prevent serious complications. Inform to the doctor if you have been diagnosed with liver disorders, heart failure, high blood cholesterol levels, or hypertension before starting this treatment.This medicine has the potential to cause liver problems, so your doctor will carry out weekly liver function tests when you are taking this drug. Report to your doctor if you experience any hypersensitive reactions like itchy skin or rashes, while taking this medicine. This tablet contains lactose as an inactive ingredient in which the body is unable to digest lactose, a sugar found in milk and dairy products. It can cause symptoms such as bloating, and abdominal pain. If you have lactose intolerance, inform your doctor before starting this therapy.

It is advised to consult the physician if you experience fever, sore throat, jaundice, nausea, vomiting, signs of local infection, bleeding from any site, or symptoms suggestive of anaemia. Women of childbearing potential should be advised to avoid becoming pregnant. It is not recommended for pregnant women as it may cause fetal harm. Consult your doctor if you are pregnant or planning for pregnancy during the treatment. This medicine passes into the breast milk. Hence, it is not recommended to breastfeed during this treatment. It is recommended to limit your alcohol intake or avoid it altogether during the treatment. While you are taking this drug, you are more sensitive to the sun and UV light. Just make sure to limit your exposure to sunlight and UV light, wear protective clothing and use a sun cream with a high sun protection factor (SPF). Low blood sugar (sweating more than usual, nausea, dizziness, confusion, etc.) has sometimes been seen in children, mainly in children under the age of six or with a low body mass index. Talk to your child's doctor if this happens.

1. Aspen Pharma Trading Limited, Electronic medicines compendium (EMC), [ Revised on August 2019] (Accessed: April 6, 2023), https://www.medicines.org.uk/emc/files/pil.4655.pdf
2. Purinethol® (mercaptopurine) 50-mg scored tablets caution. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/009053s032lbl.pdf (Accessed: April 6, 2023).
3. Goodman & Gilman’s, The Pharmacological Basis of Therapeutics, Cytotoxic agents, 12th edition, 2011, 1701 - 1702.
4. KD Tripathi, Essentials of Medical Pharmacology, Anticancer drugs, 7th edition, 2013, 863.

The drug information on this page is not a substitute for medical advice, it is meant for educational purposes only. For further details consult your doctor about your medical condition to know if you are eligible to receive this treatment.