Mercaptopurine (patient information)

# About your treatment
Your doctor has ordered the drug mercaptopurine to help treat your illness. The drug is taken by mouth in tablet form.
This medication is used to treat:
- leukemia
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
Mercaptopurine belongs to a group of drugs known as antimetabolites. It resembles a normal cell nutrient needed by cancer cells to grow. The cancer cells take up mercaptopurine which then interferes with their growth.

# Other uses for this medicine
Mercaptopurine is also used to treat many types of autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, acute idiopathic polyneuritis, acute idiopathic nephrotic syndrome, psoriatic arthritis, erythroid aplasia, or myelofibrosis; idiopathic hemolytic anemia; macroglobulinemia; idiopathic thrombocytopenia purpura; idiopathic pulmonary hemosiderosis; multiple sclerosis; myasthenia gravis; uveitis; and ulcerative colitis. Talk to your doctor about the possible risks of using this drug for your condition.

# Precautions
Before taking mercaptopurine:
- tell your doctor and pharmacist if you are allergic to mercaptopurine or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially allopurinol (Zyloprim), anticoagulants ('blood thinners') such as warfarin (Coumadin), aspirin, and vitamins.
- you should know that mercaptopurine may interfere with the normal menstrual cycle (period) in women and may stop sperm production in men. However, you should not assume that you cannot get pregnant or that you cannot get someone else pregnant. Women who are pregnant or breast-feeding should tell their doctors before they begin taking this drug. You should not plan to have children while receiving chemotherapy or for a while after treatments. (Talk to your doctor for further details.) Use a reliable method of birth control to prevent pregnancy. Mercaptopurine may harm the fetus.
- do not have any vaccinations (e.g., measles or flu shots) without talking to your doctor.

# Side effects

## Minor side effects
Side effects from mercaptopurine are common and include:
- headache
- weakness or achiness
- darkening of the skin
- loss of appetite or weight
Tell your doctor if either of these symptoms is severe or lasts for several hours:
- mouth blistering
- fatigue

## Severe side effects
If you experience any of the following symptoms, call your doctor immediately:
- painful urination or red urine
- black, tarry stools
- diarrhea
- pain in the abdomen
- unusual bruising or bleeding
- shortness of breath
- swelling of the feet or legs
- cough
- fever
- sore throat
- nausea and vomiting
- rash
- yellowing of the skin or eyes
- joint pain
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online  or by phone .

# Special instructions
Drink plenty of fluids. Drink about 10 eight-ounce glasses of fluid and urinate frequently during the first 24 hours after treatment to keep your kidneys working. 
The most common side effect of mercaptopurine is a decrease in the number of blood cells. Your doctor may order tests before, during, and after your treatment to see if your blood cells are affected by the drug.

# Brand names
- Purinethol

# Other names
- 6-MP