Aflibercept (Zaltrap) | Cancer Research UK
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What aflibercept is 

Aflibercept (pronounced ay-flib-er-set) is also called Zaltrap. It is a treatment for advanced bowel cancer. It is licensed for advanced bowel cancer in combination with the chemotherapy combination FOLFIRI. You can usually only have aflibercept if you have already had the chemotherapy drug oxaliplatin.


How aflibercept works

Aflibercept stops cancers making blood vessels. Doctors call this anti angiogenesis treatment. All cells, including cancer cells, need to develop blood vessels so that they can grow. Aflibercept blocks 3 proteins that cells need to develop blood vessels. So the cancer can't grow.


How you have aflibercept

You have aflibercept into your bloodstream (intravenously). You can have it through a thin, short tube (a cannula) put into a vein in your arm each time you have treatment. Or you may have it through a central line, a portacath, or a PICC line. These are long, plastic tubes that give the drugs directly into a large vein in your chest. You have the tube put in before or during your course of treatment and it stays in place as long as you need it.

You can read our information about having chemotherapy into a vein.

The aflibercept drip takes 1 hour each time. If you are having it with other chemotherapy you usually have this after the aflibercept. You have the treatment every 2 weeks for as long as it is working.


Tests during treatment

You have blood tests before starting treatment and regularly during your treatment. The tests check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.


About side effects

We've listed the side effects associated with aflibercept. You can use the links to find out more about each side effect. Where there is no link, please go to our information about cancer drug side effects or use the search box at the top of the page.

You may have a few side effects. They may be mild or more severe. A side effect may get better or worse through your course of treatment. Or more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)

The side effects may be different if you are having aflibercept with other medicines.

Tell your doctor or nurse straight away if any of the side effects get severe.


Common side effects

More than 10 in every 100 people have one or more of these side effects

  • An increased risk of getting an infection from a drop in white blood cells — it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, a sore throat, pain passing urine, or you may feel cold and shivery. If you have a severe infection this can be life threatening. Contact your treatment centre straight away if you have any of these effects or if your temperature goes above 38°C
  • Tiredness and breathlessness from a drop in red blood cells (anaemia) — you may need a blood transfusion
  • Bruising more easily from a drop in platelets — you may have nosebleeds, or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechiae)
  • Diarrhoea — drink plenty of fluids and tell your doctor or nurse if you are worried about how bad it is or if it continues for more than 3 days
  • Tiredness and weakness (fatigue) occurs in 6 in 10 people (60%) during and after treatment — most people find their energy levels are back to normal within 6 months to a year
  • Protein in the urine (proteinuria) occurs in 6 in 10 people (60%) — your nurse will test your urine regularly. If it contains protein you will need to do a 24 hour urine collection to check your kidneys are working normally
  • Feeling or being sick affects about 5 out of 10 people (50%) — this is usually well controlled with anti sickness medicines
  • A sore mouth happens in around 5 out of 10 people (50%)
  • Blood pressure may be higher than normal in 4 out of 10 people (40%)
  • Loss of appetite and weight loss occurs in 3 out of 10 people (30%)
  • Abdominal (tummy) pain
  • Constipation happens in 2 out of 10 people (20%) — your doctor or nurse may give you medicines to help prevent this. Tell them if you are constipated for more than 3 days
  • A hoarse voice
  • Headaches
  • Weakness
  • Soreness, redness and peeling on the palms of the hands and soles of the feet (palmar-plantar syndrome). This may cause tingling, numbness, pain and dryness
  • Liver changes that are very mild and unlikely to cause symptoms — the liver will almost certainly go back to normal when treatment ends
  • Loss of fertility — you may not be able to become pregnant or father a child after this treatment. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment

Occasional side effects

Between 1 and 10 in every 100 people have one or more of these side effects

  • An allergic reaction during the treatment – let your nurse know if you feel hot or have any skin rashes, itching, dizziness, headaches, or shivering. Also let them know if you have breathlessness, anxiety, flushing of the face, or a sudden need to pass urine
  • Development of an abnormal opening between parts of the body, for example between the gut and the skin or between the gut and the bladder. These are called fistulas and may leak fluid. If you notice this tell your doctor or nurse straight away
  • Blood clots happen in fewer than 1 out of 10 people (10%) — if you have any clots, you will have treatment to thin your blood, dissolve them and stop more developing
  • Toothache

Rare side effects

Fewer than 1 in 100 people have these side effects

  • A split in the wall of the bowel (bowel perforation) – if this happens it is serious so let your doctor or nurse know straight away if you have a sudden, severe pain in the tummy (abdomen) and feel faint
  • A group of symptoms including headaches, seizures (fits), changes in eye sight, excessive sleepiness, changes in behaviour, and possibly high blood pressure. Doctors call this group of symptoms Reversible Posterior Leucoencephalopathy Syndrome (RPLS)
  • Watery eyes from increased production of tears
  • Damage to the jaw bone (osteonecrosis of the jaw) – have a dental check and any necessary dental treatment before starting aflibercept. During treatment keep your mouth clean and have routine dental check ups. Report any loose teeth, mouth or jaw pain or swelling. Avoid dental procedures during treatment where possible

Important points to remember

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. They can give you advice or reassure you. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Other medicines

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Don't breastfeed during this treatment because the drug may come through in the breast milk.

Slow wound healing

Aflibercept can slow down wound healing. If you need to have an operation your doctor will normally advise you to stop having it for a while beforehand. They will let you know when you can start having it again.



You shouldn't have immunisations with live vaccines while you are having this treatment or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG, yellow fever and Zostavax (shingles vaccine).

You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your treatment. It is safe to have the flu vaccine.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with vaccines you take by mouth (oral vaccines), but not many people in the UK have these now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.


Related information


More information about aflibercept treatment

We don't list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect we don't mention here and you think it may be due to this treatment, you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 3 November 2015