Avonex Side Effects

Avonex is a form of protein called beta interferon that occurs naturally in the body. Interferons help the body fight viral infections.

Avonex is used to treat patients with relapsing forms of multiple sclerosis to slow the accumulation of physical disability. This medication will not cure MS, it will only decrease the frequency of relapse symptoms.

Do 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.

If you have any of these other conditions, you may need a dose adjustment or special tests:

  • liver disease;
  • epilepsy or other seizure disorder;
  • heart disease, chest pain (angina), congestive heart failure, or a heart rhythm disorder;
  • a thyroid disorder; or
  • a history of depression or suicidal behavior.

FDA pregnancy category C. 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 become pregnant during treatment. It is not known whether interferon beta-1a passes into breast milk or if it could harm a nursing baby. Do not use Avonex without telling your doctor if you are breast-feeding a baby.

Get emergency medical help if you have any of these signs of an allergic reaction to Avonex: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have a serious side effect such as:

  • depressed mood, anxiety, trouble sleeping, restlessness, or thoughts of suicide or hurting yourself;
  • easy bruising or bleeding, weakness;
  • seizure (convulsions);
  • numbness or tingling in your hands or feet;
  • pain or burning when you urinate;
  • pain, swelling, or skin changes where the injection was given;
  • fever, chills, body aches, flu symptoms; or
  • nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Less serious Avonex side effects may include:

  • headache, dizziness;
  • stomach pain; or
  • runny or stuffy nose.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.