Before taking mercaptopurine,
tell your doctor and pharmacist if you are allergic to mercaptopurine, any other medications, or any of the ingredients in mercaptopurine tablets or suspension. Ask your pharmacist for a list of the ingredients.
tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: allopurinol (Lopurin, Zyloprim); aminosalicylates such as mesalamine (Apriso, Asacol, Canasa, Lialda, Delzicol, Pentasa, others), olsalazine (Dipentum), and sulfasalazine (Azulfidine); anticoagulants ('blood thinners') such as warfarin (Coumadin, Jantoven); doxorubicin (Doxil); and trimethoprim and sulfamethoxazole (Bactrim, Septra). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
tell your doctor if you have already taken mercaptopurine or thioguanine to treat your cancer. Your doctor may tell you not to take mercaptopurine if either of these medications did not work well against your cancer in the past.
tell your doctor if you have any type of infection and if you have or have ever had liver or kidney disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. You should use birth control to avoid pregnancy during your treatment with mercaptopurine. If you become pregnant while taking mercaptopurine, call your doctor immediately. Mercaptopurine may harm the fetus.
if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking mercaptopurine.
do not have any vaccinations without talking to your doctor.
you should know that the risk that you will develop serious side effects of mercaptopurine may be higher if you have a genetic (inherited) risk factor. Your doctor may order tests before or during your treatment to see if you have this risk factor.