Thioguanine

What is thioguanine?

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

You may hear thioguanine called 6-TG, or by its brand name Lanvis. Thioguanine comes in a tablet form.

Before giving thioguanine to your child

Tell your child's doctor if:

• your child has ever reacted badly to thioguanine or to any other medication, food, preservatives, or colouring agents
• your child has ever been treated with thioguanine or mercaptopurine in the past

Talk with the doctor or pharmacist if your child has any of the following conditions. Precautions may need to be taken with this medicine if your child has:

• infection or recent exposure to infection (for example chickenpox)
• liver or kidney problems
• low blood counts
• thiopurine methyltransferase deficiency (TPMT)

How should you give your child thioguanine?

Follow these instructions when you give your child this medicine:

• Give your child thioguanine for as long as your doctor or pharmacist tells you, even if your child seems better. Talk to your child's doctor before you stop giving this medicine for any reason.
• Give your child thioguanine at the same time and the same way (either with or without food) each day it is prescribed.
• If your child has difficulty swallowing thioguanine tablets, review the options with the pharmacist. Tablets should NOT be crushed.
• Consider wearing gloves and a mask when handling thioguanine. 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 thioguanine?

• 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 2 doses to make up for 1 missed dose.

What are the possible side effects of thioguanine?

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

• loss of appetite
• weight loss
• loose stools (diarrhea)
• mild nausea (upset stomach) and vomiting (throwing up)
• skin rash or itching

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

• joint pain
• swelling of feet or lower legs
• unsteadiness when walking
• sores in mouth and on lips
• yellow eyes or skin
• sudden weight gain

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
• cough or sore throat
• severe diarrhea
• severe abdominal pain
• black, tarry stools
• blood in urine or stools
• difficulty with urination or pain with urination
• lower back or side pain
• pinpoint red spots on skin
• unusual bruising or bleeding

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

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

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

Tell your doctor or dentist that your child is receiving thioguanine before your child has any operation, even on the teeth, or an emergency treatment.

Thioguanine 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 should not touch your child's eyes or inside the nose without washing hands first.
• Your child's nurse will review with you what to do in case of fever.

Thioguanine 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.
• Be careful when shaving or waxing.
• Your child should avoid contact sports where bruising or injury could occur.
• Your child should not receive a permanent tattoo or any kind of body piercing.
• Before your child has surgery, including dental surgery, inform the doctor or dentist that your child is taking thioguanine.

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. Other live vaccines that your child should not get include measles, mumps and rubella (MMR) and chicken pox vaccine.

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

There is a chance that thioguanine 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 thioguanine. 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 thioguanine?

• Thioguanine does not normally cause hair loss.
• 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.
• Thioguanine may make your child's skin more likely to sunburn. Make sure your child covers their skin and head with clothing and a hat. Or use a strong sunscreen (a cream that protects the skin from the sun). Look for a sunscreen that says it protects against the sun's ultraviolet rays, called UVA and UVB rays. The sunscreen should have a sun protection factor (SPF) of at least 15. Ask your pharmacist to help you pick the right sunscreen.
• Make sure you always have enough thioguanine to last through weekends, holidays, and vacations. Call your pharmacy at least 2 days before your child runs out of medicine to order refills. Not all pharmacies will carry thioguanine.
• Keep thioguanine 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 thioguanine out of your child’s sight and reach and locked up in a safe place. If your child takes too much thioguanine, 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.