A new warning has been issued about the controversial multiple sclerosis drug Tysabri (natalizumab). U.S. health officials have announced that the medication, manufactured by Biogen Idec and Elan Corporation, can begin causing liver damage within six days of the first dose.
The liver damage caused by Tysabri can be fatal and may result in the need for a liver transplant. Use of the drug should be stopped if patients become jaundiced or have other evidence of liver damage.
This is not the first time that the adverse effects of Tysabri have been in the spotlight. The drug first received approval from the U.S. Food and Drug Administration (FDA) in November 2004, but was pulled from the market three months later after several patients in clinical trials developed a deadly viral infection of the brain called progressive multifocal leukoencephalopathy. In June 2006, the FDA allowed the drug back on the market but with strict administration guidelines.