Mercaptopurine

What is mercaptopurine?

Mercaptopurine is a medicine used to kill cancer cells. It stops the cells from dividing and making new cells.

You may hear mercaptopurine called 6-MP, or by its brand name Purinethol. Mercaptopurine comes in tablet form.

Before giving mercaptopurine to your child

Tell your doctor if your child has ever reacted badly to mercaptopurine or any other medicines, foods, preservatives, or colouring agents.

Talk with the doctor or pharmacist if your child has any of the following conditions. This medicine may not be right for your child if they have:

• infection or recent exposure to infection (such as chickenpox)
• very low blood counts
• liver or kidney problems

How should you give your child mercaptopurine?

Follow these instructions when you give your child this medicine:

• Give your child mercaptopurine exactly as the doctor or your pharmacist tells you to. Talk to your child's doctor before you stop giving this medicine for any reason.
• Give your child mercaptopurine at the same time and the same way (either with or without food) each day it is prescribed.
• Check what dose your child is supposed to get and be sure that is the dose your child receives. Sometimes the dose may be different on different days of the week. Your child's doctor, nurse, or pharmacist can work with you to make sure your child's dose schedule is clear.
• If your child is not taking a whole mercaptopurine tablet or has problems swallowing tablets, review the options with your pharmacist. Tablets should NOT be crushed.
• Consider wearing gloves and a mask when handling mercaptopurine. Always wash your hands after each dose that you give your child.
• If your child vomits (throws up) within 20 to 30 minutes of taking a dose, give another dose. If your child vomits again, do not give any further doses. Contact the doctor or clinic nurse the next morning to let them know.

What should you do if your child misses a dose of mercaptopurine?

• Give the missed dose as soon as you remember.
• If it is almost time for the next dose, skip the missed dose. Give the next dose at the regular time.
• Do not give your child two doses to make up for one missed dose.

What are the possible side effects of mercaptopurine?

Your child may have some of these side effects while they take mercaptopurine. Check with your child's doctor if your child continues to have any of these side effects and they do not go away, or if they bother your child:

• nausea (upset stomach) or vomiting (throwing up)
• darkening of skin
• loss of appetite
• diarrhea (loose, watery bowel movements)
• headache
• skin rash and itching
• weakness
• mouth sores

Call your child's doctor during office hours if your child has any of these side effects:

• unusual tiredness or weakness
• yellow skin or eyes
• joint pain
• swelling of the feet or lower limbs

Most of the following side effects are not common, but they may be a sign of a serious problem. Call your child's doctor right away or take your child to Emergency if your child has any of these side effects:

• fever or chills
• sore throat or cough
• lower back or side pain
• pinpoint red spots on skin
• pain or burning with urination
• black, tarry stools
• blood in the urine or stools
• unusual bleeding or bruising

What safety measures should you take when your child is using mercaptopurine?

Keep all appointments at the clinic or doctor's office so that the doctor can check your child's response to mercaptopurine. The doctor may need to change the dose of mercaptopurine from time to time so that your child is getting the right amount.

Your child's doctor will order blood tests to check for problems with the liver and blood while your child is getting mercaptopurine.

Tell the doctor or dentist that your child is taking mercaptopurine before your child has any kind of operation, even on the teeth, or an emergency treatment.

Your child's skin may darken while receiving mercaptopurine, especially on elbows and knees and in skin creases. If this happens, it will slowly fade once your child stops taking mercaptopurine.

Mercaptopurine may cause sores in the mouth. Rinse your child's mouth with a mouthwash made from baking soda to help keep it clean. Your child's nurse or pharmacist can review this with you. Avoid store-bought mouthwash containing alcohol, as it may sting and cause dry mouth.

Mercaptopurine can lower the number of white blood cells in the blood temporarily, which increases your child's chances of getting an infection. Your child can take the following precautions to prevent infections, especially when the blood count is low:

• Avoid people with infections, such as a cold or the flu.
• Avoid places that are very crowded with large groups of people.
• Be careful when brushing or flossing your child's teeth. Your doctor, nurse or dentist may suggest different ways to clean your child's mouth and teeth.
• You and your child shouldn't touch your child's eyes or inside their nose without washing hands first.
• Your child's nurse will review with you what to do in case of fever.

Mercaptopurine can lower the number of platelets in the blood, which increases your child's risk of bleeding. You can take the following precautions:

• Be careful not to cut your child when using a razor, fingernail scissors, or toenail clippers.
• Your child should avoid contact sports where bruising or injury could occur.
• Before your child has surgery, including dental surgery, inform the doctor or dentist that your child is taking mercaptopurine.
• Your child should not receive a permanent tattoo or any kind of body piercing.

Your child should not receive any immunizations (vaccines) without your child's doctor's approval. Your child or anyone else in your household should not get oral polio vaccine while your child is being treated for cancer. Tell your child's doctor if anyone in your household has recently received oral polio vaccine. Your child should avoid contact with anyone who has recently received this vaccine.

There is a chance that mercaptopurine may cause birth defects if it is taken at the time of conception or if it is taken during pregnancy. If your child is sexually active, it is best that they use some kind of birth control while receiving mercaptopurine. Tell the doctor right away if your child may be pregnant.

Check with your child's doctor or pharmacist before giving your child any other medicines (prescription, non-prescription, herbal, or natural products).

What other important information should you know about mercaptopurine?

• Hair loss does not usually occur with mercaptopurine.
• Keep a list of all medications your child is on and show the list to the doctor or pharmacist.
• Do not share your child's medicine with others and do not give anyone else's medicine to your child.
• Make sure you always have enough mercaptopurine to last through weekends, holidays, and vacations. Call your pharmacy at least two days before your child runs out of medicine to order refills. Not all pharmacies will carry mercaptopurine.
• Keep mercaptopurine at room temperature in a cool, dry place away from sunlight. Do NOT store it in the bathroom or kitchen.
• Do not keep any medicines that are out of date. Check with your pharmacist about the best way to throw away outdated or leftover medicines.
  

Keep mercaptopurine out of your child’s sight and reach and locked up in a safe place. If your child takes too much mercaptopurine, call your local Poison Information Centre at one of these numbers. These calls are free. 

• Call 1-844 POISON-X, or 1-844-764-7669, from anywhere in Canada except Quebec.
• Call 1-800-463-5060 if you live in Quebec.