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Interferon (Intron A)

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This page tells you about the biological therapy interferon alpha and its possible side effects. There are sections about


What interferon is

Interferon alpha is a man made copy of a substance that some types of white blood cell make naturally in the body. The blood cells make interferon as part of the immune response when the body reacts to infection or to cancer.

Interferon is also called interferon alfa. It is used to treat several different types of cancer, including 

  • Kidney cancer (renal cell cancer)
  • Malignant melanoma
  • Multiple myeloma
  • Some types of leukaemia

It is also used to treat conditions other than cancer.


How interferon works

Interferon works in several ways. It interferes with cancer cells and stops them growing and multiplying. It also stimulates the immune system by encouraging killer T cells and other cells to attack cancer cells. It can encourage cancer cells to send out chemicals that attract immune system cells to them.

You can read about the immune system and cancer.


How you have interferon

Interferon is most often given by injection just under the skin (subcutaneously) into the abdomen (tummy) or thigh. How often you have it depends on which cancer you have. It can be given daily, although it is most often given 3 times a week.

If you are having interferon for some weeks or months, a nurse may teach you to give the injection yourself at home. Or a family member can learn how to do it. You need to keep your interferon in the fridge.

Sometimes interferon is given into the bloodstream or by injection. You can have it through a thin, short tube (a cannula) put into a vein in your arm. 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 can read our information about having chemotherapy into a vein.

The side effects associated with interferon alpha are listed below. You can use the links (underlined) to find out more about each side effect. Where there is no link, the information in the cancer drugs side effects section may be helpful. Or you can use the search box at the top of the page.


Common side effects

More than 10 in every 100 people have one or more of the side effects listed below.

  • Pain, redness, itching or swelling at the injection site (with injections just under the skin)
  • Hair thinning – this is more likely to happen with long courses or high doses of interferon
  • Dizziness
  • Loss of appetite – this may increase as your course of treatment goes on
  • 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. You will have regular blood tests to check your blood cell levels
  • Tiredness and breathlessness due to a drop in red blood cells (anaemia) – you may need a blood transfusion
  • Bruising more easily due to 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 petechia
  • Tiredness and weakness (fatigue) during and after treatment – most people find that their energy levels are back to normal from 6 months to a year after their treatment ends
  • Flu like symptoms can occur, including fever, chills, a headache, and aching muscles and joints – nearly everyone taking interferon has this side effect at first. It usually gets better as your course of treatment continues. These symptoms usually begin 2 to 4 hours after your injection and last for about 12 hours. Take paracetamol before your injection and every 4 to 6 hours afterwards for as long as you need to. But don't take more than 8 tablets in 24 hours. You can try having your injection and paracetamol before you go to bed to see if that helps
  • Pain in the tummy (abdomen)
  • Diarrhoea – you should drink plenty of fluids. If diarrhoea is severe or continues you could get dehydrated, so tell your doctor or nurse
  • Feeling or being sick – this happens to about 5 out of 10 people (50%). Your nurse will give you anti sickness medicines. Let them know if the sickness is not controlled as you could try other anti sickness drugs
  • Depression or emotional changes such as anxiety – let your doctor or nurse know if you have this
  • Difficulty sleeping
  • A sore throat and pain on swallowing
  • Headaches
  • Weight loss
  • Itchy, dry skin or rashes
  • Coughing
  • Sudden sharp muscle, joint or bone pain – let your doctor or nurse know if you have this

Occasional side effects

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

  • Drowsiness or dizziness
  • Liver changes that are mild and unlikely to cause symptoms – the liver will almost certainly go back to normal when treatment ends. You will have regular blood tests to check how well your liver is working
  • Damage to heart muscle, which is usually temporary. For a small number of people the changes may be permanent. Your doctor will check your heart before and after your treatment
  • 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
  • Women may stop having periods (amenorrhoea) – this may only be temporary
  • An allergic reaction to the drug – let your doctor or nurse know straight away if you have swelling of the hands, feet, ankles, face, lips, mouth, or throat or any difficulty in swallowing or breathing
  • Feeling thirsty and a dry, sore mouth – drink plenty of fluids and brush your teeth at least twice a day to prevent dental problems
  • High blood pressure
  • Worsening of migraines
  • Low sex drive
  • Indigestion (heartburn)
  • Constipation
  • Swollen glands
  • Flushed skin
  • Vaginal dryness
  • Breast pain
  • Testicular pain
  • Taste changes or a metallic taste in your mouth
  • Inflammation of the sinuses causing a stuffy nose
  • Sore, red eyes
  • Sleep walking
  • Increased sweating
  • An increased need to pass urine

Rare side effects

Fewer than 1 in 100 people have these effects.

  • Fine shaking movements
  • A feeling of pins and needles

Important points to remember

The side effects above 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)
  • Other drugs you are having

Coping with side effects

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. Talk to your doctor or nurse about effective contraception before starting treatment. Women must not become pregnant for at least 4 months after the end of treatment. Men should not father a child for at least 7 months after treatment. 


Do not breastfeed during this treatment because the drug may come through in the breast milk.

Children and adolescents

Children and young people may grow and develop more slowly during interferon treatment.



You should not have immunisations with live vaccines while you are having 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.


More information about interferon

This information does not list all the very rare side effects of interferon alfa that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 11 February 2015