Tysabri for Treating Multiple Sclerosis

Safety Considerations When Taking This Immunosuppressant

Tysabri (natalizumab) is a prescription immunomodulator drug used to treat multiple sclerosis (MS). With this disease, the immune system damages the myelin that coats your nerves, not allowing them to work properly. Tysabri prevents certain immune cells in your bloodstream from crossing the blood-brain barrier, which helps protect the myelin in your brain and spinal cord from being damaged.

Saline intravenous (iv)
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Tysabri is used as a disease-modifying therapy, which means it's intended to slow the progression of the disease rather than to manage symptoms. It's approved by the U.S. Food and Drug Administration (FDA) for people with relapsing forms of MS, as well as for Crohn's disease.

It's generally prescribed for people who:

  • Don't respond to other disease-modifying therapies, which means their disease continues to worsen
  • Can't tolerate other MS drugs, usually because of harmful or bothersome side effects

While Tysabri is shown to be effective, it isn't considered a first-line treatment because, in rare cases, it can cause a potentially fatal brain infection (see below).


Tysabri is FDA-approved for relapsing-remitting MS (RRMS).

Numerous studies have demonstrated the drug's effectiveness in RRMS, with the benefits being:

  • Reduced relapse rate as high as 68% over two years
  • Slower disability progression
  • Prolonged remissions

A study of Tysabri in patients with SPMS did not show any benefit in slowing disability progression measured by a combination of tests; however, there was some suggestion of benefit in slowing the loss of function of the upper extremities. Further studies are needed to confirm this finding.


Tysabri is a monotherapy, meaning it's not combined with other MS medications.

The drug is administered as an infusion (given through your vein) once every 28 days. You have to go to an infusion center, or sometimes a healthcare provider's office, to have it done.

Side Effects

Common side effects of Tysabri include:

If any of these side effects become especially bothersome or don't go away, let your healthcare provider know.

More serious side effects are possible. If you experience or suspect any of the following, you should contact your healthcare provider immediately:

  • Herpes infection in the central nervous system: Symptoms include sudden fever, severe headache, and confusion; can be fatal
  • Herpes infection of the eye: Symptoms include changes in vision, redness, and eye pain; may cause blindness
  • Liver damage: Symptoms include yellow skin and eyes, dark urine, nausea, feeling tired or weak, and vomiting
  • Allergic reaction: Symptoms include hives, itching, trouble breathing, chest pain, dizziness, chills, rash, nausea, flushing of the skin, low blood pressure, and possibly anaphylaxis

Important Warnings

The most serious (but rarest) risk of taking Tysabri is progressive multifocal leukoencephalopathy (PML), which is a potentially fatal brain infection caused by the John Cunningham (JC) virus. You also need to be aware that there can be consequences when you start and then stop Tysabri.


Factors that increase your risk of getting PML while taking Tysabri include:

  • Combining Tysabri with other medications that weaken the immune system
  • Taking Tysabri for more than two years
  • Testing positive for the JC virus antibody

To determine your risk, expect your healthcare provider to test your blood for the antibody to the JC virus prior to prescribing Tysabri and depending on the results, repeating them on a periodic basis. Based on the results, your healthcare provider will determine the risk/benefit ratio for you.

In addition, you'll probably have an magnetic resonance imaging (MRI) scan before starting the drug. This is to help your healthcare provider distinguish between MS symptoms and possible PML symptoms.

PML symptoms include: 

  • Gradual weakness on one side of the body
  • Clumsiness
  • Vision changes
  • Personality changes
  • Problems with thinking, memory, and orientation leading to confusion

Tysabri can only be given at an infusion center that is registered through the TOUCH program. TOUCH stands for "Tysabri Outreach: Unified Commitment to Health." It was put in place to help prevent PML and catch potential cases in the early stages. 

The Rebound Effect

Another concern with Tysabri is the phenomenon known as rebound. Basically, if you stop taking the drug, MS relapse symptoms can return, and, in some cases, be worse than before you started treatment.

A 2014 study concluded that interrupting Tysabri therapy was linked to a nearly two-fold increase in the risk of relapse. A quarter of participants also had more relapses after stopping Tysabri than before treatment was started.

Why this happens and how to prevent it are unclear.

If you want to discontinue Tysabri, be sure to discuss it with your healthcare provider and carefully consider the possible ramifications.


You shouldn't take Tysabri if you're pregnant or want to become pregnant. While its effect in humans is unknown, Tysabri has caused fetal harm in animal studies. You should go off of Tysabri a few months before trying to conceive, so be sure to talk to your healthcare provider about your plans.

Also inform your healthcare provider if you are nursing or plan to. Tysabri does pass through breast milk, but whether or not it can have an effect on your baby is unknown.

Don't combine Tysabri with immunosuppressants, immunomodulators, or the corticosteroid Solu-Medrol.

Finally, don't take Tysabri if you have a compromised immune system or a current infection.


Tysabri is an expensive MS treatment at $6,864 a month, plus the cost of the infusion center. Your insurance may cover some or all of this.

Additionally, the manufacturer offers programs that may help you afford this treatment. For more information, you can call the company at 1-800-456-2255 or visit their website.

A Word From Verywell

You will have to work closely with your healthcare provider to decide if Tysabri is the right medication for you, making sure to weigh all the risks and benefits. It's a difficult process, but in the end, the goal is to find the treatments that work best for you—and that's a worthwhile goal.

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Tysabri (natalizumab) website. Important Safety Information.

Additional Reading

By Julie Stachowiak, PhD
Julie Stachowiak, PhD, is the author of the Multiple Sclerosis Manifesto, the winner of the 2009 ForeWord Book of the Year Award, Health Category.