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Drugs reference index «Avonex»



Generic Name: interferon beta-1a (Intramuscular route, Subcutaneous route, Injection route)

in-ter-FEER-on BAY-ta-1a

Commonly used brand name(s):

In the U.S.

  • Avonex
  • Rebif

Available Dosage Forms:

  • Solution
  • Kit

Therapeutic Class: Immunological Agent

Pharmacologic Class: Interferon, Beta (class)

Uses For Avonex

Interferon beta-1a 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.

Before Using Avonex

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 this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


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.


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.


Pregnancy CategoryExplanation
All TrimestersCAnimal studies have shown an adverse effect and there are no adequate studies in pregnant women OR no animal studies have been conducted and there are no adequate studies in pregnant women.

Breast Feeding

Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.

Interactions with Medicines

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Rotavirus Vaccine, Live

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Zidovudine

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Alcohol abuse or
  • Higher concentration of a liver enzyme called SGPT
  • Liver disease, active or in the past—This medicine should be used cautiously. You should tell your doctor if you have any of these conditions. If you start having symptoms of liver problems such as jaundice (yellow skin and eyes), tell your doctor right away; your medicine may need to be stopped.
  • Heart disease—Some side effects of this medicine may be harmful to patients with serious heart problems
  • Mental depression or thoughts of suicide or
  • Psychiatric disorders or
  • Other mood disorders—This medicine may make the condition worse
  • Seizure disorder—The risk of seizures may be increased

Proper Use of interferon beta-1a

This section provides information on the proper use of a number of products that contain interferon beta-1a. It may not be specific to Avonex. Please read with care.

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.


The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • 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) or 44 mcg 3 times a week, injected under the skin; your doctor may start you at a lower dose at first.
      • 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 possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

The next injection should be scheduled at least 48 hours later.


Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

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.

Precautions While Using Avonex

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.

Importance of caretaker and/or patient informing doctor of any signs or symptoms of depression or other mental or mood disturbances.

Check with your doctor right away if you experience dark urine, persistent loss of appetite, yellow eyes or skin, influenza (flu)-like symptoms, right upper quadrant tenderness, headache, stomach pain, continuing vomiting, general feeling of tiredness or weakness, or light-colored stools. These could be symptoms of serious liver problems.

You should avoid alcohol while you are taking this medicine. It can cause serious liver problems.

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.

Avonex Side Effects

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
  • Black, tarry stools
  • chest pain
  • chills
  • cough
  • diarrhea
  • fever
  • flu-like symptoms including headache, joint pain, muscle aches, and nausea
  • pain
  • painful or difficult urination
  • shortness of breath
  • sores, ulcers, or white spots on lips or in mouth
  • swollen glands
  • 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
  • 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
Incidence not known
  • Bleeding gums
  • blood in urine or stools
  • bloody nose
  • chest discomfort
  • confusion
  • constipation
  • continuing vomiting
  • convulsions
  • dark urine
  • decreased urine output
  • depressed mood
  • dilated neck veins
  • dry skin and hair
  • extreme fatigue
  • faintness
  • fast, irregular, or pounding heartbeat
  • feeling cold
  • general tiredness and weakness
  • hair loss
  • heavier menstrual periods
  • high fever
  • hoarseness or husky voice
  • irregular breathing
  • light-colored stools
  • loss of bladder control
  • mental depression
  • mood or other mental changes
  • muscle cramps and stiffness
  • muscle spasm or jerking of all extremities
  • nausea and vomiting
  • nervousness
  • pale skin
  • persistent anorexia
  • pinpoint red spots on skin
  • pruritus
  • puffiness or swelling of the eyelids, or around the eyes, face, lips, or tongue
  • redness, blistering, peeling, or loosening of the skin
  • right upper quadrant tenderness
  • sensitivity to heat
  • shortness of breath
  • skin rash
  • slowed heartbeat
  • stomach pain
  • sudden loss of consciousness
  • sweating
  • swelling of face, fingers, feet, or lower legs
  • swelling of the mouth or throat
  • tightness in chest
  • tightness in throat
  • upper right abdominal pain
  • vesicular rash
  • weight gain
  • weight loss
  • yellow eyes and skin

Some 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. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
  • Heartburn
  • indigestion
  • sour stomach
Less common
  • Hair loss
  • trouble in sleeping

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

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

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  • Avonex Consumer Overview
  • Avonex Prefilled Syringes MedFacts Consumer Leaflet (Wolters Kluwer)
  • Avonex Prescribing Information (FDA)
  • Interferon Beta-1a Professional Patient Advice (Wolters Kluwer)
  • Interferon Beta-1a MedFacts Consumer Leaflet (Wolters Kluwer)
  • Rebif Prescribing Information (FDA)
  • Rebif Consumer Overview

See Also...

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