Summary Safety Review - AVONEX (interferon beta-1a) - Assessing the Potential Risk of Kidney Damage (nephrotic syndrome)

Review decision

A Summary Safety Review complements other safety related information to help Canadians make informed decisions about their use of health products. Each summary outlines what was assessed in Health Canada’s review, what was found and what action was taken by Health Canada, if any.

Issued: 2015-12-23


Avonex (interferon beta-1a)

Potential Safety Issue

Assessing the Potential Risk of Clots in Small Blood Vessels (thrombotic microangiopathy)

Key Messages

  • Avonex is used to treat some forms of multiple sclerosis, a disease of the central nervous system.
  • A safety review was triggered when Health Canada identified a possible risk of clots in small blood vessels (thrombotic microangiopathy) with Avonex treatment, during a routine review of information received from the manufacturer.
  • Health Canada considers that after reviewing the totality of evidence available at this time, there is a potential risk of thrombotic microangiopathy with Avonex. Health Canada has therefore asked the manufacturer to update the Canadian prescribing information for Avonex to include this risk.


Health Canada carried out a safety review to look into the potential risk of thrombotic microangiopathy with the use of Avonex. This issue was found during the review of new safety information given by the manufacturer.

Use in Canada

  • Avonex is used to treat some forms of multiple sclerosis, to reduce damage to the central nervous system, and to slow down the worsening of the disease. Avonex is given by injection into the muscle at a dose of 30 micrograms once a week.
  • Avonex has been marketed in Canada since December 2005. It is available by prescription only.

Safety Review Findings

  • Thrombotic microangiopathy is a group of serious life-threatening conditions involving the formation of clots in the small blood vessels. These clots can cause damage to organs and body systems by blocking proper blood flow.
  • There are two forms of interferon beta sold in Canada to treat multiple sclerosis: Type 1a (Avonex and Rebif) and Type 1b (Betaseron and Extavia).
  • The manufacturer provided a report from the Avonex Global Safety Database, which had cases of thrombotic microangiopathy that were possibly caused by Avonex. The review of these cases was limited by many factors like other pre-existing diseases, other medications taken, and a possible confusion of thrombotic microangiopathy with other causes of organ damage. Nonetheless, a link between Avonex and the development of thrombotic microangiopathy could not be ruled out.
  • At the time of the review, information regarding the risk of thrombotic microangiopathy was already included in the Canadian prescribing information for Rebif, but not for Avonex.

Conclusions and actions

  • Health Canada's safety review considers that there is a potential risk of thrombotic microangiopathy with Avonex, given the current evidence and reported cases.
  • In addition, thrombotic microangiopathy has been linked to other interferon beta drugs and currently appears in the Canadian prescribing information for Rebif.
  • Since there may be a possible link between Avonex and thrombotic microangiopathy, Health Canada requested that the manufacturer update the Canadian prescribing information to include this risk.
  • Health Canada will continue to monitor side effect information involving Avonex, as it does for all health products on the Canadian market, to identify and assess potential harms. Health Canada will take appropriate and timely action if and when any new health risks are identified.

Additional information

The analysis that was carried out for this safety review took into consideration information from scientific and medical literature, Canadian and international adverse reaction reports as well as what is known about the use of this drug in Canada and internationally.

For additional information, contact the Marketed Health Products Directorate.