FDA wants prescribing information on Tysabri updated

WASHINGTON The Food and Drug Administration said Monday that prescribing instructions for the multiple sclerosis drug Tysabri should be changed to inform users of cases of the brain disorder progressive multifocal leukoencephalopathy in some patients using the drug.

The FDA said that two patients using Tysabri alone to treat MS developed the disorder, but that the risk might be lower for patients using only Tysabri than for patients using it in combination with similar medications.

Tysabri is marketed by Biogen Idec and Ireland-based Elan and is known generically as natalizumab.