Irinotecan is a chemotherapy medicine used for the treatment of certain types of cancer. This page from Great Ormond Street Hospital (GOSH) explains what irinotecan is, how it is given and some of the possible side effects. Irinotecan is given as an injection into a vein (intravenously or IV) through a cannula, central venous catheter or implantable port in hospital.

What are the side effects?


Diarrhoea (runny poo), sometimes severe, can develop on the day your child has irinotecan or longer afterwards. The doctor will prescribe an anti-diarrhoeal medicine called loperamide which you will need to give exactly as explained. You should also follow general guidance for reducing the risk of diarrhoea and dehydration, such as making sure your child drinks plenty of fluids.

If your child continues to have diarrhoea or is not drinking fluids, you should watch for signs of dehydration, which include:

  • Extreme thirst
  • Dry and hot skin
  • Dry nappies for more than six hours
  • Drowsiness
  • Fainting
  • Fast heartbeat
Dehydration can quickly become serious in children so contact your doctor or nurse immediately as your child may need to have fluids as an intravenous infusion (drop) or may need antibiotics.

Acute cholinergic syndrome

Some people develop symptoms that are described as acute cholinergic syndrome. These can include tummy cramps, diarrhoea, sweating, runny nose, watery eyes, increased drooling, reduction in the size of the eye pupils and flushing. These symptoms can be controlled or prevented by an injection of a medicine called atropine.

Nausea and vomiting

Anti-sickness drugs can be given to reduce or prevent these symptoms. Please tell your doctor or nurse if your child’s sickness is not controlled or persists.

Bone marrow suppression

There will be a temporary reduction in how well your child’s bone marrow works. This means that they may become anaemic, bruise or bleed more easily than usual and have a higher risk of infection.

Your child’s blood count will be examined regularly to check how well the bone marrow is working. Please tell your doctor if your child seems unusually tired, has bruising or bleeding or any signs of infection, especially a high temperature.

Mouth sores and ulcers

You will be given advice about appropriate mouth care including a copy of the mouth care leaflet. If your child complains about having a sore mouth, please tell your doctor or nurse.

Loss of appetite

Your child may ‘go off’ food and their appetite may be reduced during treatment. The dietitian at the hospital will be able to suggest ways of making food more attractive to your child.


Your child may feel a bit more tired than usual. If you are concerned, please tell your doctor or nurse.

Changes in liver function

Irinotecan can cause some mild changes to your child’s liver function. This will return to normal when the treatment is finished. Blood tests may be taken to monitor your child’s liver function.

Hair loss

Your child may lose all their hair, including their eyebrows and eyelashes, or they it may become thinner. This is temporary and the hair will grow back once the treatment has finished.

Less common side effects

Children may also develop other side effects although these are less common. Possible side effects include constipation, raised blood pressure and allergic reactions to the medicine.

Interactions with other medicines

Some medicines can react with irinotecan altering how well it works. Always check with your doctor or pharmacist before giving your child any other medicine, including medicines on prescription from your family doctor (GP), medicines bought from a pharmacy (chemist) or any herbal or complementary medicines (for example St John’s Wort).

Compiled by:
The Pharmacy team in collaboration with the Child and Family Information Group
Last review date:
April 2020