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Interferon Beta-1a (By injection)

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

Treats multiple sclerosis (MS).

Brand Name(s):

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

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to interferon beta or human albumin.

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 on the same 3 days each week, 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. Follow instructions to mix. 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 a dose of the prefilled syringe or Rebif® Rebidose® autoinjector, throw away any medicine that is leftover. Do not reuse needles or syringes.
  • Missed dose:
    • Avonex®: Give the dose as soon as you remember. Go back to your regular schedule the following week. Do not use extra medicine to make up for a missed dose. Do not use this medicine 2 days in a row.
    • Rebif®: Give the dose as soon as you remember. Skip the next day and give your next regular dose 48 hours later. Go back to your regular schedule the following week. Do not use extra medicine to make up for a missed dose. Do not use this medicine 2 days in a row.
  • Keep this medicine in the refrigerator if you store it at home. Do not freeze. You may allow the prefilled autoinjector pens and prefilled syringes to warm to room temperature for 30 minutes before injection. Do not heat in a microwave oven or in hot water.
  • 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 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.
  • Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.

Drugs and Foods to Avoid:

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

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have liver disease, bone marrow or bleeding problems, heart disease, heart failure, heart rhythm problems, or thyroid problems. Tell your doctor if you have a history of alcohol abuse, depression, or seizures. Tell your doctor if you have a latex allergy.
  • This medicine may increase depression or thoughts of suicide. Tell your doctor right away if you start to feel more depressed or think about hurting yourself.
  • This medicine may cause the following problems:
    • Liver problems
    • Seizures
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Wash your hands often.
  • Some forms of this medicine are made from donated human blood. All donated blood is tested for certain viruses. Although your risk for getting a virus from the medicine is very low, talk with your doctor if you have concerns.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

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, trouble breathing, uneven heartbeat
  • Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
  • Fever, chills, cough, sore throat, body aches
  • Seizures
  • Swollen or tender glands in the neck, armpit, or groin
  • Unusual bleeding, bruising, or weakness
  • Unusual moods or behaviors, depression, thoughts of hurting yourself or others

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

  • Muscle or joint pain
  • Pain, burning, redness, swelling, or blue or black skin where the shot was given

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

Last Updated: 8/28/2020

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