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Generic Name: interferon beta-1a (in ter FEAR on BAY ta)
Brand Names: Avonex, Rebif

Medically reviewed on Jan 15, 2018

What is Avonex?

See also: Aubagio

Avonex (interferon beta-1a) is made from human proteins. Interferons help the body fight viral infections.

Avonex is used to treat relapsing multiple sclerosis (MS). This medication will not cure MS, it will only decrease the frequency of relapse symptoms.

Avonex may also be used for purposes not listed in this medication guide.

Important information

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Avonex may be harmful to an unborn baby, or may cause a miscarriage. Do not use Avonex if you are pregnant. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Before using Avonex, tell your doctor if you are allergic to any drugs, or if you have liver disease, a thyroid disorder, epilepsy or other seizure disorder, heart disease, chest pain (angina), congestive heart failure, a heart rhythm disorder, or a history of depression or suicidal behavior.

Before using Avonex

You should not use Avonex if you are allergic to interferons or human albumin.

Some patients using interferon medications have become very depressed or had thoughts of suicide. Stop using Avonex if you have symptoms of depression (sadness, crying, loss of interest in things you once liked) or if you have any thoughts of hurting yourself.

To make sure Avonex is safe for you, tell your doctor if you have:

  • liver disease;

  • epilepsy or other seizure disorder;

  • heart disease, chest pain (angina);

  • a bleeding disorder or history of blood clots;

  • a thyroid disorder; or

  • a history of depression or suicidal behavior.

Avonex may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

It is not known whether interferon beta-1a passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Some brands of interferon beta-1a contain albumin. Albumin comes from human plasma (part of the blood) which may contain viruses and other infectious agents. Donated plasma is tested and treated to reduce the risk of it containing infectious agents, but there is still a small possibility it could transmit disease. Talk with your doctor about the risks and benefits of using this medication.

How should I use Avonex?

Use Avonex exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Avonex is injected into a muscle. It is usually given once weekly at bedtime, on the same day each week (such as every Monday). Follow your doctor's instructions.

You may be shown how to use injections at home. Do not self-inject this medicine if you do not fully understand how to give the injection and properly dispose of used needles and syringes.

Avonex comes with patient instructions for safe and effective use. Follow these directions carefully. Ask your doctor or pharmacist if you have any questions.

Use a different place on your body each time you give the injection. Your care provider will show you the best places on your body to inject the medication. Do not inject into the same place two times in a row.

The powder form of Avonex must be mixed with a liquid (diluent) in the medicine vial. Gently swirl but do not shake the vial after mixing the medicine. The mixture should be clear or light yellow. Do not use the mixture if it has changed colors or has any particles in it. Mix a new dose or call your doctor for a new prescription.

Do not draw your dose into a syringe until you are ready to give yourself an injection.

Each prefilled syringe or single use vial (bottle) of this medicine is for one use only. Throw away after one use, even if there is still some medicine left after injecting your dose.

Use a disposable needle only once, then throw away in a puncture-proof container (ask your pharmacist where you can get one and how to dispose of it). Keep this container out of the reach of children and pets.

Avonex can lower blood cells that help your body fight infections and help your blood to clot. This can make it easier for you to bleed from an injury or get sick from being around others who are ill. Your blood may need to be tested often. Your liver or thyroid function may also need to be tested.

Store Avonex in a refrigerator. Do not freeze. You may take the Avonex prefilled syringe out of the refrigerator and allow it to reach room temperature before giving the injection. Do not heat the medicine before using.

Avonex may be kept at room temperature for short periods if protected from light. Avonex powder can be stored at room temperature for up to 30 days. Avonex prefilled syringes can be stored at room temperature for only 7 days.

After mixing Avonex powder with a diluent, store in the refrigerator and use it within 6 hours.

Throw away any Avonex that has become frozen or has been exposed to light or high heat.

What happens if I miss a dose?

Call your doctor for instructions if you miss a dose of this medication.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid?

Avoid drinking alcohol. It may increase your risk of liver damage.

Avoid being near people who are sick or have infections. Tell your doctor at once if you develop signs of infection.

Avonex side effects

Get emergency medical help if you have any signs of an allergic reaction to Avonex: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • fever, chills, body aches, chest pain, flu symptoms;

  • pale skin, easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;

  • severe pain, swelling, bruising, redness, oozing, or skin changes where the injection was given;

  • changes in your vision;

  • seizure (convulsions);

  • feeling hot or cold, unexplained weight changes;

  • kidney problems - blood in your urine, swelling or rapid weight gain, little or no urination;

  • signs of a serious blood cell disorder - confusion, feeling tired or irritable, stomach pain, bloody diarrhea, vomiting;

  • liver problems - nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or

  • severe skin reaction - fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common Avonex side effects may include:

  • stomach pain;

  • flu symptoms;

  • headache, drowsiness;

  • abnormal liver function tests; or

  • minor irritation where the injection was given.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Avonex?

Avonex can harm your liver. This effect is increased when you also use other medicines harmful to the liver. Many other drugs (including some over-the-counter medicines) can be harmful to the liver, and not all are listed here:

  • acetaminophen (Tylenol), aspirin, gout or arthritis medication (including gold injections); an NSAID (nonsteroidal anti-inflammatory drug) - ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib, diclofenac, indomethacin, meloxicam, and others;

  • an antibiotic, antifungal medicine, or sulfa drug; tuberculosis medicine; antiviral or HIV/AIDS medication; medicine to treat mental illness; seizure medication - carbamazepine, phenytoin, valproic acid, and others;

  • birth control pills or hormone replacement therapy; anabolic steroids - methyltestosterone, "performance-enhancing drugs"; cancer medication; or

  • cholesterol-lowering medication - Crestor, Lipitor, Vytorin, Zocor, and others; heart or blood pressure medication.

This list is not complete. Other drugs may interact with interferon beta-1a, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Avonex only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

More about Avonex (interferon beta-1a)

Consumer resources

Other brands: Rebif, Rebif Rebidose

Professional resources

Other Formulations

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