Natalizumab (Tysabri) is a treatment for people with relapsing forms of MS. It makes flares happen less often and keeps physical disabilities from getting worse quickly.
Tysabri works in a different way from other multiple sclerosis drugs. It keeps the white blood cells of the immune system from entering the brain and spinal cord, which doctors think plays an important role in the damaging effects of MS.
After the FDA first approved Tysabri, the drug's manufacturer took it off the market due to reports of a rare but serious brain infection called PML (progressive multifocal leukoencephalopathy). The company introduced a program that requires everyone taking the medicine to register and to follow up every so often in order to find any possible cases of PML as soon as possible. With these safety programs in place, the drug went back on the market.
Your risk for PML goes up with the number of doses you take. It’s also higher for people who’ve taken drugs that turn down their immune systems before they use Tysabri. Because of this risk, doctors usually recommend Tysabri only for people who’ve tried other MS treatments that haven’t worked.
Besides PML and allergic reactions, other serious side effects include liver damage and serious infections.
Talk with your doctor about these side effects and whether Tysabri would be a good option for you. Together you can weigh the risks and benefits and decide if you should take the drug.