Azathioprine; Mercaptopurine/Methotrexate Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Methotrexate may slow down how your body processes azathioprine and mercaptopurine.

What might happen:

The amount of some types of blood cells in your blood may decrease and your liver may be damaged.

What you should do about this interaction:

Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. Your doctor may need to perform laboratory tests of your blood cells, and adjust the dose of one or both medicines. Let your doctor know right away if you develop persistent nausea/vomiting, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine or have any signs of an infection (such as fever, persistent sore throat), or easy bruising or bleeding, black or tarry stools, blood in urine, or mouth or lip sores.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

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  • 2.Innocenti F, Danesi R, Di Paolo A, Loru B, Favre C, Nardi M, Bocci G, Nardini D, Macchia P, Del Tacca M. Clinical and experimental pharmacokinetic interaction between 6-mercaptopurine and methotrexate. Cancer Chemother Pharmacol 1996;37(5):409-14.
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  • 4.Rheumatrex (methotrexate, oral) US prescribing information. Dava Pharmaceuticals, Inc. February, 2013.
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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.