Interferon beta-1a belongs to a group of medications known as immunomodulators. It is a form of a protein that is naturally made by our body's cells to fight infections and tumours.

Interferon beta-1a is used to treat relapsing forms of multiple sclerosis (MS), a chronic and disabling disease that affects the central nervous system by destroying the protective covering (myelin) surrounding nerve fibres. This medication is also used to delay the onset of MS in people who have experienced a single flare-up of symptoms and have changes that suggest MS in their magnetic resonance imaging (MRI) scans.

Interferon beta-1a will not cure MS but may decrease the number of flare-ups of the disease, slow the progression of disability, and decrease the number and volume of active brain lesions (damaged areas of the brain) seen in the MRI scans.

This medication can also be used to treat people with another type of MS known as secondary progressive MS (SPMS) who are still having relapses. For people with SPMS, the medication can decrease the frequency of relapses and reduce brain lesions seen on MRI scans.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

The usual adult dose of interferon beta-1a for people with relapsing forms of MS is 30 µg once a week as an injection into a muscle (thigh or upper arm) on the same day of the week (e.g., every Saturday right before bedtime). For people with relapsing progressive MS or secondary progressive MS with recurrent attacks, your doctor may increase the dose to 60 µg once a week.

To reduce flu-like symptoms at the start of treatment, your doctor may start treatment at a lower dose, and gradually increase the dose weekly over three to six weeks. Your doctor may also recommend a medication for pain or fever to be taken before the injection and for 24 hours after the injection each week, to decrease flu-like side effects.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

Interferon beta-1a is used with the guidance and supervision of a doctor. Your doctor or nurse may ask you to inject the medication at home once they have instructed you and are certain that you won't have any problems with doing it at home. Do not attempt to prepare or inject this medication on your own until you completely understand how to prepare the syringe and inject a dose.

Make sure that you change your injection site each week. You should avoid injecting this medication into an area of skin that is sore, red, infected, or otherwise damaged. If you are having difficulty giving yourself injections, talk to your health care provider.

It is important to use this medication exactly as prescribed by your doctor. If you miss a dose, inject it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not inject a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice. Do not take this medication 2 days in a row.

Prefilled syringes of interferon beta-1a must be stored in the refrigerator. Remove the syringe from the refrigerator about 30 minutes before use to allow the medication to reach room temperature. Do not use external heat sources (such as hot water or a microwave) to warm up the medication. The prefilled syringe must be used within 7 days of removing it from the refrigerator.

Please refer to the package insert for complete instructions on using this medication. Always wash your hands before preparing the medication and after you have used it. Always use a new unopened vial, syringe, and needle. Never reuse vials, syringes, prefilled syringes, or needles.

Protect this medication from light, moisture, freezing, and high temperatures. Keep this medication out of the reach of children.

Avonex PS

Each prefilled syringe of sterile liquid contains 30 µg (6.0 million IU) of interferon beta-1a. Nonmedicinal ingredients: arginine hydrochloride USP, glacial acetic acid USP, polysorbate 20, sodium acetate trihydrate USP, and water for injection USP 0.5 mL at a pH of 4.8.

Avonex Pen

Each prefilled single-use autoinjector of sterile liquid contains 30 µg (6.0 million IU) of interferon beta-1a. Nonmedicinal ingredients: arginine hydrochloride USP, glacial acetic acid USP, polysorbate 20, sodium acetate trihydrate USP, and water for injection USP 0.5 mL at a pH of 4.8.

Do not use this medication if you are allergic to interferon beta-1a or any ingredients of the medication.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain
• decreased appetite
• diarrhea
• difficulty sleeping
• dizziness
• flu-like symptoms (fever, chills)
• hair loss
• headache
• heartburn
• muscle aches
• nausea
• skin irritation, swelling, or pain at the injection site
• tiredness or weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• chest tightness
• chills or fever
• shortness of breath
• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of bleeding (low levels of platelets; e.g., bloody nose, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
• signs of infection (decreased numbers of white blood cells; e.g., fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of heart problems (e.g., decreased ability to exercise, increased heart rate, shortness of breath, swollen ankles, tightness in the chest)
• signs of liver problems (e.g., abdominal pain, dark urine or pale stools, easy bruising, yellow eyes or skin)
• signs of thyroid problems (e.g., changes in sleep patterns, feeling constantly hot or cold, weight changes)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• seizures
• signs of a serious allergic reaction (e.g., difficulty breathing; hives; swelling of the face, tongue, or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic reactions: In rare cases, some people may develop a severe allergic reaction to this medication. Signs of an allergic reaction include a severe rash, hives, swollen face or throat, or difficulty breathing. If these occur, contact your doctor immediately. The needle cover on the prefilled syringe contains dry natural rubber. Before you start injections, tell your doctor if you have an allergy to rubber or latex.

Blood counts: This medication can decrease the number of neutrophils (a type of white blood cell that helps fight infection), red blood cells (which carry oxygen), and platelets (which help your blood to clot). Your doctor will do blood tests to monitor this. If you notice any signs of infection (e.g., fever, chills, or sore throat) or unusual bleeding or bruising, contact your doctor immediately.

Depression: Depression has been reported by some people taking interferon medications. If you have a history of depression, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. People with depression should be closely monitored by their doctor. If you develop symptoms of depression such as poor concentration, changes in weight, changes in sleep, decreased interest in activities, or thoughts of suicide while taking this medication, contact your doctor as soon as possible.

Heart problems: This medication may worsen symptoms of heart disease. If you have heart disease such as angina, congestive heart failure, or arrhythmia, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Contact your doctor as soon as possible if you develop symptoms of heart problems such as shortness of breath, chest pain, rapid heartbeat, or swollen ankles.

Liver damage: This medication may cause severe liver damage. Although rare, this side effect can be very serious. If you have a history of poor liver function, alcohol abuse, or active liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor will test your liver function regularly while you are taking this medication. Contact your doctor as soon as possible if you notice any of the signs of liver damage, including yellow eyes or skin, easy bruising of the skin, nausea and vomiting, itching, or abdominal pain.

Seizures: Some people have had seizures while taking this medication, including people who have never had seizures before. It is not known whether the seizures were related to the effects of their MS, the medication, or the combination of both. If you have seizure disorder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you have a seizure while taking this medication, you should call your doctor right away.

Thyroid problems: Some people taking this medication develop changes in the function of their thyroid. Symptoms of these changes include feeling cold or hot all the time, a change in weight (gain or loss) without a change in your diet or amount of exercise you get, or feeling emotional. Contact your doctor if you experience these symptoms.

Pregnancy: This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately. Women who may become pregnant should use effective contraception while taking this medication.

Breast-feeding: It is not known if interferon beta-1a passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children and adolescents less than 18 years of age.

There may be an interaction between interferon beta-1a and any of the following:

• cladribine
• natalizumab
• zidovudine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.