On February 27, 2008, Biogen Idec notified healthcare professionals that clinically significant liver injury has been reported in patients taking Tysabri. Signs of liver injury, which may lead to death or the need for a liver transplant, occurred as early as six days after the first dose.

These warnings were added to the “Warnings and Precautions” section of the Tysabri labels. In addition, the companies instructed healthcare professionals to inform their patients that Tysabri may cause acute liver failure.

For more information, contact Biogen Idec at 1-800-456-2255, or visit the company’s website.

Source: “Tysabri: Important Safety Information,” Food and Drug Administration Release, February 2008.