Tysabri (generic: natalizumab) is a prescription medication used to treat multiple sclerosis and Crohn's disease. Tysabri belongs to a group of drugs called immunomodulators. It is thought to work by stopping certain cells of the immune system from reaching the brain and spinal cord or digestive tract and causing damage.

This medication comes in an injectable form to be given once every four weeks through a needle placed in a vein (IV infusion).

Common side effects of Tysabri include headache, tiredness, and joint pain. Because Tysabri can cause serious side effects, this medication is only available through a special program called the Touch program.