Avonex injection contains the active ingredient interferon beta-1a, which is a type of medicine called an immunomodulator.

What is it used for?

  • Relapsing/remitting multiple sclerosis in people who have had at least two relapses over the previous three years.
  • Treatment of patients who have experienced a single multiple sclerosis-like attack, severe enough to need treatment with intravenous corticosteroids, if alternative diagnoses have been excluded and they are at high risk of developing clinically definite multiple sclerosis.

How does it work?

  • Avonex injection contains the active ingredient interferon beta-1a, which is a type of medicine called an immunomodulator.
  • Interferons are a family of small protein molecules that are produced by cells in response to viral infections or various synthetic and biological inducers. Three major classes of interferons have been identified: alfa, beta and gamma.
They work in a complicated way that is not fully understood, but are thought to influence the way the immune system works.
  • Interferon beta is used to treat multiple sclerosis (MS). MS is a condition in which the immune system attacks the myelin sheath that surrounds the nerve fibres in the brain and spinal cord. This causes inflammation that stops the nerves working properly.
  • In most people with MS, the disease initially follows a course of relapse and remission, where symptoms worsen for a while, then improve before worsening again. It is not fully understood how interferon beta works in MS, but it has been shown to help reduce the number and severity of the relapses, presumably by changing the way the immune system works.
  • Some people experience a single clinical event that indicates they have a high risk of developing multiple sclerosis. In these people interferon beta has been shown to delay progression to definite multiple sclerosis.
  • Interferon beta is not effective in all people with multiple sclerosis and, because it can have significant side effects, it is recommended that all patients are assessed by a neurologist before starting treatment.
  • The medicine does not cure MS and it is not known how long treatment should be continued for. However, it is recommended that patients should be clinically evaluated after two years of treatment. You may develop neutralising antibodies to this medicine that make it less effective. The medicine should be stopped if your MS becomes progressively worse despite treatment.
  • How is this treatment given?

    • Avonex injection is given once a week, on the same day each week.
    • The injection is administered into the muscle of the upper, outer thigh. A different site should be used each week.
    • The injections can be given by your doctor or nurse, or by yourself or your carer after you have been carefully trained. Always use this medicine exactly as your doctor has told you. Check with your doctor, pharmacist or nurse if you are not sure.
    • Carefully follow the instructions provided with your injections.

    Not to be used in

    • Children under 12 years of age.
    • People with severe depression or thoughts of suicide.
    • Pregnancy.
    • Breastfeeding.

    This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

    If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

    Use with caution in

    • People with a history of depression or suicidal thoughts.
    • People with a history of seizures, eg due to brain injury or epilepsy, particularly people with epilepsy that is not well controlled by antiepileptic medicines.
    • People with severely decreased kidney function.
    • People with severely decreased liver function or a history of liver disease.
    • People who drink large amounts of alcohol.
    • People with a history of an overactive or underactive thyroid gland.
    • People with heart disease such as angina, heart failure or irregular heartbeats (arrhythmias).
    • People with low levels of red blood cells (anaemia), white blood cells or platelets (thrombocytopenia) in their blood.

    Pregnancy and breastfeeding

    • This medicine should not be started in women who are pregnant because it may be harmful to a developing baby and may increase the risk of miscarriage.
    • Women who could get pregnant should use an effective method of contraception to prevent pregnancy while having treatment with this medicine. If you get pregnant during treatment or want to try for a baby you should consult your doctor immediately for medical advice.
    • It is not known if this medicine passes into breast milk. The manufacturer states that it should not be used during breastfeeding. Alternatively, breastfeeding can be stopped. This decision will depend on the importance of the medicine to the mother. Seek medical advice from your doctor.

    Side effects

    Very common

    • Headache.
    • Flu-like symptoms such as aches and pains, fever, chills, sweating and headache. These tend to be worse at the start of treatment and improve with continued treatment. 


    • Injection site reactions such as pain, redness or bruising.
    • Flushing.
    • Increased sweating.
    • Feeling weak or tired.
    • Rash.
    • Runny nose.
    • Pain in the muscles, joints, back or neck.
    • Muscle cramps or stiffness.
    • Loss of sensation (numbness).
    • Gut disturbances, such as diarrhoea, nausea or vomiting.
    • Difficulty sleeping (insomnia).
    • Depression. 
    • Loss of appetite.
    • Disturbance in the normal numbers of blood cells in the blood. 


    • Hair loss (alopecia).
    • Heavy or irregular menstrual bleeding.


    • Small blood clots in the blood vessels that could affect your kidney function (thrombotic microangiopathy). You should tell your doctor if you experience unusual bruising or bleeding, a high temperature (fever), confusion, muscle weakness or a rise in your blood pressure while having treatment with this medicine, as these could be symptoms of this condition.
    • Shortness of breath.
    • Kidney disorder called nephrotic syndrome.
    • Frequency not known
    • Weight changes.
    • Fast or irregular heartbeat or awareness of your heartbeat (palpitations).
    • Heart failure.
    • Dizziness or fainting.
    • Seizures (convulsions).

    The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

    How can this medicine affect other medicines?

    • No formal interaction studies have been conducted with this medicine.
    • There may be an increased risk of side effects on the liver or blood cells if other medicines that can affect the liver or blood cells are used in combination with this one.

    This medicine may increase the blood level of certain other medicines, such as the following:

    • antiepileptic medicines
    • zidovudine.











    Health Reference: Multiple sclerosis