Gemtuzumab is used to treat a type of leukaemia. It is often given in combination with medicines called mitoxantrone and cytarabine. Gemtuzumab is a ‘biologic’ medicine, that is, it is a manmade version of a naturally occurring antibody. It works by targeting proteins on the surface of cancer cells so that they die. This page from Great Ormond Street Hospital (GOSH) explains what gemtuzumab is, how it is given and some of the possible side effects.

In the UK, gemtuzumab is currently unlicensed for children and young people aged less than 15 years. Medicines are often used outside of their license (off-label) in children because clinical trial data is not available for a specific use. Prescribing medicines ‘off label’ is not necessarily hazardous but should be explained and agreed before use.

How is it given?

Gemtuzumab is given as an infusion into a vein (intravenously or IV), through a cannula, central venous catheter or implantable port. Blood tests will be needed before each infusion.

Antihistamine medicines to stop an allergic reaction are given one hour before the infusion is started. Corticosteroid medicine and paracetamol is also be given at this point.

Effects on the unborn child

Gemtuzumab must not be given to girls who may be pregnant or are likely to become pregnant in the near future. If your daughter is ten years old or older, we will ask her about her periods and any possibility that she could be pregnant. We will also carry out a pregnancy test on a fresh urine sample. If your daughter is sexually active, she must use a reliable form of contraception.

What are the side effects?

Allergic reaction

Some people receiving gemtuzumab have an allergic reaction to the medicine. This reaction may be mild to severe.

Signs of a mild allergic reaction include skin rashes and itching, high temperature, shivering, redness of the face, a feeling of dizziness or headache. If you see any of these signs, please report them to a doctor or nurse.

Signs of a severe allergic reaction include any of the above, as well as shortness of breath. If you are in hospital and your child shows signs of a severe allergic reaction, call a doctor or nurse immediately.

Altered blood counts

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

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

Increased risk of infection

Tell the doctor if your child has any signs of infection, such as a high temperature, sore throat, upset tummy or pain when weeing. In most cases, they are not serious but it is best to check.

Liver function

Gemtuzumab can have an effect on how the liver works. This will be monitored with regular blood tests (liver function tests or LFTs) throughout treatment.

Fluid retention

If you notice any swelling or puffiness around your child’s limbs, especially the ankles, please tell your doctor or nurse.


This can be a sign of fluid building up around the lungs. If your child develops a cough, breathing difficulties and/or chest pain, tell your doctor immediately.


Tell the doctor if your chlid has a headache as the dose of pain relief may need to be increased.

Upset stomach, nausea and vomiting

Anti-sickness medicines can be given to reduce or prevent these symptoms. Please tell your doctor or nurse if your child’s sickness is very bad or lasts for more than a few days.

If your child has been prescribed anti-sickness medicine, they should have a dose 30 minutes before each dose of gemtuzumab.

Skin rashes and blistering

This is rare but could be serious. If your child develops any redness to their skin or blisters and a raised temperature, tell your doctor immediately.

Raised levels of uric acid in the blood

As the leukaemia cells die, uric acid is released from these cells which can crystallise causing damage to the kidneys. Another medicine called allopurinol stops these crystals from forming.

Interactions with other medicines

Some medicines can react with gemtuzumab, 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.


Alert card

We recommend that your child carries a biological therapy alert card at all times. This could be important if your child needs emergency treatment for any reason.

Chicken pox

If your child is on gemtuzumab and has not had chickenpox but comes into contact with someone who has chicken pox or shingles (either face to face or longer than 15 minutes in the same room), you should report to your doctor immediately as your child may be at risk of developing a more severe form of the infection an may need special treatment. If your child gets chicken pox or shingles you should also report to your doctor immediately for antibiotics to be given. If you are unsure whether your child has had chicken pox prior to starting gemtuzumab, their immunity should be checked with a simple blood test at that time and the result entered on the parent-held monitoring card.


Your doctor will advise you if your child should avoid immunisation during treatment. Your child should NOT have any live vaccinations such as MMR, oral polio, chicken pox or BCG while taking gemtuzumab. Inactivated or killed vaccines such as influenza/flu, meningitis C, pneumococcal, hepatitis, Hib, tetanus, diphtheria, whooping cough/pertussis and the killed version of the polio immunisation are permitted if the patient is stable under treatment. If you have other children who need vaccines while your child is taking gemtuzumab, they should have these as normal, but they should also receive the ‘killed’ or inactivated polio vaccine. If you have any questions about vaccines and immunisations, please ask your doctor.

Compiled by:
The Pharmacy team in collaboration with the Child and Family Information Group
Last review date:
October 2019