Avonex is a form of the protein beta interferon, which occurs in the body. These proteins help to fight viral infections in the body. Avonex is used as treatment for relapsing forms of multiple sclerosis. Although it will not cure MS, Avonex has been known to decrease the frequency of relapse. The drug, which is manufactured by Biogen, Inc., was approved by the FDA in 1996. By 2004, Avonex had made $1.42 billion in sales and was used by more than 130,000 patients.

Recently, a warning was added to Avonex packaging which states that severe hepatic injury, or hepatic failure may occur. Hepatitis and elevated serum hepatic enzyme levels were reported in patients taking Avonex. In many cases, these injuries occurred while Avonex was being used in combination with other products or drugs such as alcohol. The FDA and manufacturers have stated that MS patients on Avonex should be monitored closely for liver problems.

In 2005, the FDA also reported that some people suffered from Progressive Multifocal Leukoencephalopathy (PML) while taking Avonex. Many people with MS take Avonex in combination with other drugs, such as Tysabri (which was taken off the market after serious side effects were discovered). There were two severe instances when Tysabri and Avonex were taken together. In one instance, the person taking the drugs died, while the other developed PML—a rare and frequently fatal disease of the central nervous system. PML often causes irreversible mental deterioration and death. Both patients had taken Avonex in combination with Tysabri for more than two years. Symptoms of PML include mental deterioration, vision loss, speech disturbances, ataxia (inability to coordinate movements), paralysis and coma.
Less serious side effects may include:

  • Headache, dizziness
  • Stomach pain
  • Runny or stuffy nose

Serious side effects may include:

  • Depressed mood, anxiety, trouble sleeping, restlessness, or thoughts of suicide or hurting yourself
  • Easy bruising, bleeding, or 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
  • Nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes)

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