Interferon Beta-1a (Injection)


Interferon Beta-1a (in-ter-FEER-on BAY-ta-1a)

Reduces frequency of relapses in people who have multiple sclerosis (MS). Also delays some of the physical disabilities caused by MS.

Brand Name(s)

Avonex, Avonex Pen, Rebif, Rebif Rebidose, Rebif Rebidose Titration Pack

When This Medicine Should Not Be Used

How to Use This Medicine


  • Your doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot under your skin or into a muscle.
  • This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
  • A nurse or other health provider will give you this medicine.
  • You may be taught how to give your medicine at home. Make sure you understand all instructions before giving yourself an injection. Do not use more medicine or use it more often than your doctor tells you to.
  • Rebif® comes as an autoinjector pen or a prefilled syringe. It works best if you use it at the same time (usually in the late afternoon or evening) on the same 3 days each week (such as Monday, Wednesday, and Friday) at least 48 hours apart.
  • Avonex® comes as a prefilled autoinjector pen, a prefilled syringe, or a powder. The powder must be mixed with sterile water before it is given. Do not shake the vial after you add the water. Gently swirl the water and medicine together to mix. The mixture should be clear or slightly yellow. Do not use the mixture if you see particles in it. Use the medicine as soon as possible after you mix it. If you cannot give your shot right away, you can keep the syringe in the refrigerator for up to 6 hours. After 6 hours, throw the medicine away and mix another dose.
  • You will be shown the body areas where this shot can be given. Use a different body area each time you give yourself a shot. Keep track of where you give each shot to make sure you rotate body areas.
  • Use a new needle and syringe each time you inject your medicine. Do not use any other needle for the prefilled autoinjector pen.
  • After you have used 1 dose of the prefilled syringe or Rebif® Rebidose® autoinjector, throw away any medicine left in the syringe or autoinjector. Do not reuse needles or syringes.

If a dose is missed:

  • If you miss a dose or forget to use your medicine, use it as soon as you can. This will then change the time for your next dose. After you use the missed dose, use your next regular dose of Rebif® 48 hours later and go back to your regular schedule the following week. For Avonex®, call your doctor if your next regular dose is less than 2 days away. For either brand, do not use extra medicine to make up for a missed dose and do not use this medicine 2 days in a row.

How to Store and Dispose of This Medicine

  • Keep this medicine in the refrigerator if you store it at home. Do not freeze. If refrigeration is not available, Rebif® prefilled syringes and Avonex® powder vials may be kept for up to 30 days at room temperature, away from heat (temperatures above 77 degrees F) and direct light. Avonex® prefilled autoinjector pens and prefilled syringes may be stored for up to 7 days at room temperature, away from heat and direct light. You may allow the prefilled autoinjector pens and prefilled syringes to warm to room temperature for 30 minutes before injection, but do not heat in a microwave oven or with hot water.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any leftover medicine, containers, and other supplies. Throw away old medicine after the expiration date has passed.
  • Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Tell your doctor if you drink alcohol regularly.

Warnings While Using This Medicine

  • Make sure your doctor knows if you are pregnant or breastfeeding or if you have liver disease, bone marrow problems, heart disease (such as cardiomyopathy), congestive heart failure, heart rhythm problems, or a history of angina, thyroid problems, or epilepsy or seizures. Tell your doctor if you have an autoimmune disorder (such as autoimmune hepatitis, idiopathic thrombocytopenia) or a history of depression or other emotional problems.
  • Tell your doctor right away if you are anxious, irritable, depressed, or have other abnormal behaviors or suicidal thoughts. This could be a serious reaction to the medicine.
  • Check with your doctor right away if you have upper stomach pain, pale stools or dark urine, or nausea and vomiting. These could be symptoms of a serious liver problem.
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Avoid people who are ill, and wash your hands often. Brush and floss your teeth gently, do not play rough sports, and be careful with sharp objects.
  • This medicine commonly causes a flu-like reaction, with aching muscles, chills, fever, headache, joint pain, and nausea. Your doctor may want you to take a medicine for pain and fever to help control these side effects.
  • Some forms of this medicine are made from donated human blood. Some human blood products have transmitted certain viruses to people who have received them, although the risk is low. Human donors and donated blood are both tested for viruses to keep the transmission risk low. Talk with your doctor about this risk if you are concerned. The Avonex® ready to use syringe and autoinjector pen do not contain albumin, which comes from donated human blood.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Change in how much or how often you urinate, difficult or painful urination
  • Chest pain or fast heartbeat
  • Dark-colored urine or pale stools, nausea, vomiting, loss of appetite, pain in your upper stomach, yellow skin or eyes
  • Depression, thoughts of hurting yourself or others
  • Seizures
  • Swelling in your hands, ankles, or feet
  • Swollen or tender glands in the neck, armpit, or groin
  • Trouble breathing, cold sweat, and bluish-colored skin
  • Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

  • Changes in vision
  • Fever, chills, cough, runny or stuffy nose, sore throat, and body aches
  • Headache, dizziness
  • Mild nausea, stomach pain
  • Muscle or joint pain
  • Pain, itching, burning, swelling, or a lump where the shot was given
  • Rash

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last reviewed on 8/4/2014

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