- Question: Many patients report feeling worse (feeling more tired, having more walking difficulties, or other symptoms) one week or a few days before the next Tysabri infusion. What do you think this could mean? Is it possible for Tysabri concentration to drop in such a little time? Or could that be a sign that a person is developing neutralizing antibodies (especially if such "cravings" did not occur from the start of Tysabri therapy, but only after a certain amount of time)? Thanks!
We do not have an adequate explanation for this phenomenon at present. If a patient is receiving Tysabri every month, receptor concentration remains well above 90 % in all patients. It is still possible that Tysabri has some direct effects on CNS cell types that follows a different time course, but this seems unlikely.