I was told the drug last in your system for approximately 6 weeks, I have it administered monthly if everything is to plan but as things come up I do occasionally have it every 5-6 weeks some times.

I don't feel anything from it anymore but I have been on tysabri for almost 10 years now though.

I don't fully understand what you mean by not feeling well either? do you mean symptoms reappear? Or you just feel ill if you don't take it every month. 

@kea21 , unless there's a specific reason to prescribe otherwise, the usual dosage is every four weeks :-

https://www.mstrust.org.uk/a-z/tysabri-natalizumab

Hi,  Thanks for the replies.
        Maybe something else is going on with me?
        Maybe just the MS progression?
        All through I still have morning headaches 
        and have a heavy headed feeling most days?
        Things just seems a little worse later in the 
        Period?
        When I do something physical within a short 
        Period I start getting somewhat dizzy sort a
        Pulsing head which then effects my legs and
         I need to sit for ten to fifteen minutes to
         Recover?    MS or Drug Or ???
         Now the weather is warming up I also have
        Issues with my walking on the humid days?

Hi K-
 I was on Tysabri  for about 10 years.  Before I started I had many active lesions from an MRI scan.  During the 10 year period  I had very few lesions detected.  I would say it diminished the MS attacks by 90 to 95%  
 I started at four weeks and moved to five weeks under the theory that it would allow my immune system into my brain  after the four weeks as to prevent the JC virus from attacking and thereby contracting PML.  I did find my symptoms worsening in that last week. 
 Since I am JC virus positive, was on it for more than two years, and had prior immuno suppressant therapy,  I was in the highest category of risk for getting PML.
 My risk was estimated at greater than one in 100. ( 1/65.)  I just recently switched to Lemtrada. Fingers crossed. 
 I believe Tysabri was a very effective Drug
For me but it wasn’t perfect. 

Hi all, I’m also on Tysabri but my infusions are on a four week basis, although I’m also Jc positive, that doesn’t come into the issue as everybody is treated on the same shedual. 

Hi,   Thanks for replies.
         I will have my first JCV test on the 27the?
         At the present time in New Zealand, Tysabri     
         Is the last line!  Unless you go back to interferons which our Government drug company is stopping anyway!
We don't have access to Lemtrada or Ocrevus etc.     Evidently they may consider Ocrevus at the next annual funding meeting next year, but it will depend on Cost?
They decide who lives and dies in this country!

Hi @kea21 Hope your doing well! Which we cannot expect on tysabri, I'm on 4weeks of infusion on tysabri . . Dealing with lot of problems I currently don't know my JC virus title hoping to get a better news on this.

Hi People,   Just curious, I was told in the beginning that Tysabri was to be administered monthly?
I am as others on a six weekly infusion, Wether it is just me or not?      I am finding that I start feeling worse comes week four/ five?
Maybe that was the reason for monthly???
I still feel it is not the wonder drug many say for me at least,but I can function unlike when trying Gilenya.