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Other drug names: A-Am An-Az B C-Ch Ci-Cz D-Dh Di-Dz E F G H I-J K-L M-Mh Mi-Mz N-Nh Ni-Nz O P-Pl Pm-Pz Q-R S-Sn So-Sz T-To Tp-Tz U-V W-Z 0-9   

Interferon, Beta-1a (Systemic)

Brand Names

In the U.S.-

  • Avonex

In Canada-

  • Avonex
  • Rebif


  • Multiple sclerosis (MS) therapy agent
  • Biological response modifier


Interferon beta-1a (in-ter-FEER-on BAY-ta) is used to treat the relapsing forms of multiple sclerosis (MS). This medicine will not cure MS, but it may slow some disabling effects and decrease the number of relapses of the disease.

Interferon beta-1a is also used to treat genital warts.

This medicine is available only with your doctor's prescription, in the following dosage form(s):

  • Injection (U.S. and Canada)

Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For interferon beta-1a, the following should be considered:

Allergies- Tell your doctor if you have ever had any unusual or allergic reaction to interferons or human albumin. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy- Interferon beta-1a has not been studied in pregnant women. However, studies in animals have shown that interferon beta-1a may cause miscarriages. Be sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding- It is not known whether interferon beta-1a passes into breast milk. Because of the possibility of serious unwanted effects in the nursing infant, it is important that you discuss the use of this medicine with your doctor if you wish to breast-feed.

Children- Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of interferon beta-1a in children with use in other age groups.

Older adults- Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of interferon beta-1a in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.

Other medicines- Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Other medical problems- The presence of other medical problems may affect the use of interferon beta-1a. Make sure you tell your doctor if you have any other medical problems, especially:
  • Heart disease-Some side effects of this medicine may be harmful to patients with serious heart problems
  • Mental depression or thoughts of suicide-This medicine may make the condition worse
  • Seizure disorder-The risk of seizures may be increased

Proper Use of This Medicine

If you are injecting this medicine yourself, use it exactly as directed by your doctor .

Special patient directions come with interferon beta-1a injection. Read the directions carefully before using the medicine. Make sure you understand:

  • How to prepare the injection.
  • Proper use of disposable syringes.
  • How to give the injection.
  • How long the injection is stable.
If you have any questions about any of this, check with your health care professional.


If you are receiving interferon beta-1a at home, follow your doctors orders or the directions on the label . If you have any questions about the proper dose of interferon beta-1a, ask your doctor.

  • For injection dosage form:
    • For multiple sclerosis (MS):
      • Adults
        • For Avonex
          • 30 micrograms (mcg) once a week, injected into a muscle.
        • For Rebif
          • 22 micrograms (mcg) 3 times a week, injected under the skin
      • Children-Use and dose must be determined by the physician.
    • For genital warts:
      • Adults
        • For Rebif
          • 3.67 micrograms (mcg) per lesion 3 times a week for 3 weeks

Missed dose-

If you miss a dose of this medicine, take it as soon as remembered. The next injection should be scheduled at least 48 hours later.


To store this medicine:

  • Keep out of the reach of children.
  • Store away from direct light.
  • Store prefilled syringes or vials of interferon beta-1a in the refrigerator. Do not freeze. If refrigeration is not available, the vials that have not been mixed with diluent may be kept for up to 30 days at room temperature, as long as the temperature does not go above 77 °F.
  • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and to check for unwanted effects.

This medicine commonly causes a flu-like reaction, with aching muscles, chills, fever, headache, joint pain, and nausea. Your doctor may ask you to take acetaminophen to help control these effects. Follow your doctor's instructions carefully about how much and when to take acetaminophen.

Side Effects of This Medicine

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

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

  • More common
    • Chills;  diarrhea;  fever;  flu-like symptoms including headache, joint pain, muscle aches, and nausea;  pain;  unusual bleeding or bruising;  unusual tiredness or weakness 

  • Less common
    • Abdominal pain;  chest pain;  clumsiness or unsteadiness;  convulsions (seizures);  coughing;  decreased hearing;  difficulty in swallowing;  dizziness;  fainting;  flushing ;  hives or itching;  mood changes, especially with thoughts of suicide;  muscle spasms;  pain or discharge from the vagina;  pelvic discomfort, aching, or heaviness;  redness, swelling, or tenderness at place of injection;  runny or stuffy nose;  skin lesions;  sneezing;  sore throat;  speech problems;  swelling of face, lips, or eyelids;  troubled breathing;  wheezing 

  • Rare
    • Earache;  general feeling of discomfort or illness;  loss of appetite;  painful blisters on trunk of body-also known as shingles;  painful cold sores or blisters on lips, nose, eyes, or genitals  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

  • More common
    • Heartburn;  indigestion;  sour stomach 

  • Less common
    • Hair loss;  trouble in sleeping 

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT