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Side effects of Interferon (Intron A)

Read about the side effects of the drug interferon for cancer.

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

Contact your doctor or nurse immediately if any of your side effects get severe or if you have signs of infection, including a temperature above 38C.

Common side effects

Each of these effects happens in more than 10 in every 100 people (more than 10%). You might have one or more of them.

You might notice bruising or sore skin around the area where you have had the injection. 

Your hair may thin. It usually begins falling out gradually within 2 to 3 weeks after treatment starts.

Your hair grows back once your treatment has finished. This can take several months and your hair is likely to be softer.

Tips

  • Use gentle hair products such as baby shampoos.
  • Don't use perms or hair colours on thinning hair.
  • Use a soft baby brush and comb thinning hair gently.
  • Pat your hair dry gently rather than rubbing.
  • Avoid using hair dryers, curling tongs and curlers.

Hair thinning is more likely to happen with long courses or high doses of interferon. 

Don’t drive or operate machinery if you have this.

You might not feel like eating and may lose weight. It is important to eat as much as you can.

Tips

  • Eating several small meals and snacks throughout the day can be easier to manage.
  • Ask your doctor to recommend high calorie drinks to sip between treatments if you are worried about losing weight.
  • Eat whatever you feel like eating rather than what you think you should eat.
  • Make up calories between treatments for the days when you really don’t feel like eating.
  • Drink plenty of fluids even if you can't eat.
  • Don't fill your stomach with a large amount of liquid before eating.
  • Try to eat high calorie foods to keep your weight up.
Talk to your dietitian about having high calorie drinks to boost your calorie intake if you need them.

Signs of an infection include headaches, aching muscles, a cough, a sore throat, pain passing urine, or feeling cold and shivery.

Contact your treatment centre straight away if you have any of these signs or if your temperature goes above 38C. Severe infections can be life threatening.

Cancer drugs can reduce the number of white blood cells in the blood. This increases your risk of infections. White blood cells help fight infections.

Your white blood cell level begins to fall after each treatment. Then it gradually goes up again.

When the level is very low it is called neutropenia (pronounced new-troh-pee-nee-ah).

You have antibiotics if you develop an infection. You might have them as tablets or as injections into the bloodstream (intravenously). To have them into your bloodstream you need to go into hospital.

Cancer treatment can cause the level of red blood cells to fall (anaemia). This makes you breathless and look pale.

Red blood cells contain haemoglobin, which carries oxygen around the body. When the level of red blood cells is low you have less oxygen going to your cells.

You can also feel tired and depressed when your blood count is low and feel better once it is back to normal. The levels can rise and fall during your treatment. So it can feel like you are on an emotional and physical roller coaster.

You have regular blood tests to check your red blood cell levels. You might need a blood transfusion if the level is very low. After a transfusion, you will be less breathless and less pale.

Tell your doctor or nurse if you feel breathless.

You might notice you:

  • bruise more easily
  • have nosebleeds
  • have bleeding gums when you brush your teeth

This is due to a drop in the number of platelets that help clot your blood.

If your platelets get very low you may have lots of tiny red spots or bruises on your arms or legs called petechiae.

Tell your doctor or nurse straight away if you have petechiae.

You'll have a platelet transfusion if your platelet count is very low. It is a drip of a clear fluid containing platelets. It takes about 15 to 30 minutes. The new platelets start to work right away. 

You might feel very tired during your treatment. It might take 6 months to a year for your energy levels to get back to normal after the treatment ends. A low red blood cell count will also make you feel tired.

You can do things to help yourself, including some gentle exercise. It’s important not to push yourself too hard. Try to eat a well balanced diet.

Talk to your doctor or nurse if you are finding the tiredness difficult to manage.

This can happen a few hours after treatment. It may include headaches, muscle aches (myalgia), a high temperature and shivering. Taking paracetamol every 6 to 8 hours can help.

Let your doctor know if you have strong tummy (abdominal) pain.

Tell your doctor or nurse if you have diarrhoea. They can prescribe medicine to help you. 

Drink at least 2.5 litres of fluid a day. This helps to keep you hydrated.

Ask your nurse about soothing creams to apply around your back passage (rectum). The skin in that area can get very sore and even break if you have severe diarrhoea.

Contact your doctor or nurse immediately if you have diarrhoea 4 or more times a day, or any diarrhoea at night.

Feeling or being sick can start a few hours after treatment and last for a few days. Anti sickness injections and tablets can control it. Tell your doctor or nurse if you feel sick. You might need to try different anti sickness medicines to find one that works.

Contact your doctor or nurse straight away if you’ve been sick more than once in a day.

Tips

  • Avoid eating or preparing food when you feel sick.
  • Avoid foods that are fried, fatty, or have a strong smell.
  • Drink plenty of liquid to stop you from getting dehydrated.
  • Relaxation techniques help control sickness for some people.
  • Ginger can help – try it as crystallised stem ginger, ginger tea or ginger ale.
  • Fizzy drinks help some people when they’re feeling sick.

Sickness happens in around 5 out of 10 people (50%) taking this drug. 

Tell your doctor or nurse if you’re feeling depressed. They can arrange for you to talk to someone and give treatment if necessary.

Talk to your doctor or nurse if you’re having problems sleeping. It can help to change a few things about when and where you sleep.

Tips

  • Go to bed and get up at the same time each day.
  • Make sure the temperature is right.
  • Spend time relaxing before you go to bed - have a bath, read or listen to music.
  • Do some light exercise each day to help tire yourself out.
  • Avoid caffeine (coffee, tea, chocolate and cola drinks) after early afternoon.
  • Have a light snack before you go to bed to stop hunger waking you up.

You might have a sore throat or pain on swallowing.  

Let your doctor or nurse know if you have headaches. They can prescribe a mild painkiller such as paracetamol for you.

A rash can also be itchy. Tell your doctor or nurse if you have a skin rash. They can prescribe medicine to stop the itching and soothe your skin.

You may get a cough while you are having treatment. 

You might feel some pain from your muscles and joints. Speak to your doctor or nurse about what painkillers you can take to help with this.

If the pain is sharp then let your doctor know straight away. 

Occasional side effects

Each of these effects happens in 1 to 10 out of every 100 people (1 to 10%). You might have one or more of them.

You may feel drowsy with this treatment. Do not operate machinery or drive if you are feeling drowsy.

The changes are usually very mild and unlikely to cause symptoms. They will almost certainly go back to normal when treatment is finished. 

You have regular blood tests throughout your treatment so your doctor can check this.

Changes to the heart muscle may happen in some people. This is usually temporary but for a small number of people might be permanent. Your doctor will check your heart before and after your treatment.

Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Men

You may be able to store sperm before starting treatment.

It can take a few months or sometimes years for fertility to return to normal. You can have sperm counts to check your fertility when your treatment is over. Ask your doctor about it.

Women

This drug can cause an early menopause. This stops you from being able to become pregnant in the future. Talk to your doctor about this before your treatment. It’s sometimes possible to store eggs or embryos before treatment.

Women might stop having periods (amenorrhoea) but this may be temporary.

This usually happens with the first or second treatment. Symptoms include a skin rash, itching, feeling hot and shivering. Other symptoms include redness of the face, dizziness, a headache, shortness of breath and anxiety.

Let your doctor or nurse know if you feel very thirsty or have dry skin. This might be due to dehydration.

Drink at least 2.5 litres of fluid a day. This helps to keep you hydrated.

Tell your doctor or nurse if you have headaches, nose bleeds, blurred or double vision or shortness of breath. Your nurse checks your blood pressure regularly. 

If you have a history of migraines, they may get worse with this treatment. Speak to your doctor if this becomes a problem. 

You may have less interest in sex with this treatment. 

Contact your doctor or pharmacist if you have indigestion or heartburn. They can prescribe you medicines to help.

Constipation is easier to sort out if you treat it early. Drink plenty of fluids and eat as much fresh fruit and vegetables as you can. Try to take gentle exercise, such as walking.

Tell your doctor or nurse if you are constipated for more than 3 days. They can prescribe a laxative.

Your lymph glands might swell with this treatment. Let your doctor or nurse know if this happens.

Your skin may appear flushed.

This drug can cause vaginal dryness. You can get vaginal moisturisers (lubricants) from your nurse or from the pharmacist.

You might get breast pain whilst having this treatment. 

You may have pain in your testicles with this treatment. 

Food may taste metallic.

Tips

  • Choose foods that have strong flavours, such as herbs, spices, marinades and sauces if all your food tastes the same.
  • Season your food with spices or herbs, such as rosemary, basil and mint.
  • Garnish cold meat or cheese with pickle or chutney.
  • Try lemon or green tea if tea or coffee taste strange.
  • Sharp tasting fizzy drinks such as lemonade or ginger beer are refreshing.
  • Some people find that cold foods taste better than hot foods.

You might have a blocked or stuffy feeling in your nose. 

Your eyes may be sore because the drugs cause a reaction on the inside of your eyelids. Or you may not be making enough tears. Your eyes can feel sore and gritty and might be red.

Tell your doctor or nurse if you have dry eyes. They can prescribe eye drops, ointments or artificial tears for you.

Warm compresses can help your eye to drain if you have an infection.

You may start sleep walking. Let your doctor know if this becomes a problem for you. 

Let your doctor or nurse know if you are sweating much more than normal.

Tips

  • Cut out coffee, tea and nicotine.
  • Cut down on alcohol.
  • Sip cold or iced drinks.
  • Wear layers of light clothing so you can take clothes off if you overheat.
  • Have layers of bedclothes to remove as you need to.
  • Wear natural fibres such as silk or cotton instead of man made fabrics.

Talk to your doctor or nurse about this.

Rare side effects

Each of these effects happens in fewer than 1 in 100 people (1%). You might have one or more of them.

You might feel like you are shaking or have tremors. 

You may get a feeling of pins and needles. Let your doctor or nurse know if this happens. 

About Interferon

More information about this treatment

We haven't listed all the very rare side effects of this treatment. For further information see the electronic Medicines Compendium (eMC) website.

You can report any side effect you have that isn’t listed here to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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