Hi Sandy and Welcome to NeuroTalk. Glad you found us, as we have an active MS forum. plus a Medications forum which may be of help to you. I do know that we have some members on Tysabri, so hopefully, they will have some info for you. Make yourself at home..
http://neurotalk.psychcentral.com/forum17.html
http://neurotalk.psychcentral.com/forum72.html