Tysabri (natalizumab) is a brand-name intravenous (IV) infusion that’s prescribed for multiple sclerosis. This article covers topics such as side effects, dosage, and how Tysabri works.

Tysabri is a biologic and belongs to a drug class called integrin receptor antagonists. The medication is not available in a biosimilar version.

Read on for more information about Tysabri. You can also refer to this article for a comprehensive look at Tysabri and its other uses.

Tysabri has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Before receiving Tysabri” section.

Multiple sclerosis (MS) is an autoimmune condition that affects the central nervous system (CNS). (Your CNS includes your brain and spinal cord.)

With MS, your immune system mistakenly attacks the myelin sheath (a protective covering) that surrounds your nerves. This can cause inflammation and loss of myelin, leading to impaired communication between the CNS and the rest of your body.

There are four main types of MS:

  • Clinically isolated syndrome (CIS): With CIS, you have a single episode of MS symptoms lasting at least 24 hours. People with CIS may eventually develop other types of MS, but some may not progress to a different type.
  • Relapsing-remitting MS (RRMS): With RRMS, you have alternating episodes of relapse (worsened symptoms) and remission (lessened symptoms).
  • Primary progressive MS (PPMS): With PPMS, you have worsened symptoms of MS over time without episodes of remission.
  • Secondary-progressive MS (SPMS): With SPMS, you have longer episodes of relapse with fewer episodes of remission. SPMS may be active or nonactive. “Active” means an MRI scan has shown worsened inflammation in the CNS, while “nonactive” means the scan has not shown worsened inflammation.

Symptoms of MS

Symptoms of MS may vary from person to person. A few examples include:

  • fatigue
  • muscle spasms or weakness
  • tingling or numbness in the face, arms, or legs
  • vision changes, such as blurred vision
  • loss of coordination
  • difficulty breathing, swallowing, speaking, or walking

Who Tysabri is prescribed for

Tysabri is prescribed to treat CIS, RRMS, or active SPMS in adults. The drug is not typically prescribed to treat PPMS.

It isn’t known whether Tysabri is safe or effective for children with MS.

Below are details about how Tysabri works to treat multiple sclerosis (MS).

The way Tysabri works

How a drug works is called its “mechanism of action.” The exact way Tysabri works for treating MS isn’t fully understood.

MS may occur due to the presence of overactive immune system cells in the CNS. Tysabri is thought to prevent these cells from entering the CNS. In this way, Tysabri may help reduce CNS damage that leads to MS symptoms.

To learn more about how Tysabri works, talk with your doctor. You can also refer to this how Tysabri works article or visit the drug manufacturer’s website.

Tysabri and children

Tysabri is not approved for use in children.

Tysabri has been shown to be effective for treating multiple sclerosis (MS). In clinical trials, Tysabri treatment slowed the worsening of MS symptoms and reduced the number of relapse episodes (periods of worsened symptoms).

To learn more about how Tysabri performed in clinical trials, talk with your doctor. You can also refer to the drug’s prescribing information or the manufacturer’s website.

Below is information about the dosage of Tysabri for multiple sclerosis (MS) in adults. However, your doctor will determine the dosage that’s best for your needs.

For more information about the drug’s dosage, you can refer to our Tysabri dosage article or the drug’s prescribing information.

Dosage

For treating MS, the usual dosage of Tysabri is 300 milligrams (mg) per dose. You’ll receive one dose every 4 weeks.

Note: In addition to treating MS, Tysabri has other uses. Keep in mind that the drug’s dosage may differ with these other uses. To learn more, talk with your doctor.

How to receive

A healthcare professional will give Tysabri as an intravenous (IV) infusion. An IV infusion is an injection into a vein that’s given over a period of time. Tysabri infusions are typically given over 1 hour.

You’ll receive Tysabri in an infusion center or clinic. The facility giving the infusion must be certified by the Tysabri Outreach: Unified Commitment to Health (TOUCH) program. After your first several doses, you’ll likely stay in the facility where you received the drug for at least 1 hour. This allows your doctor to monitor you closely for serious side effects.*

If you have questions about the TOUCH program or receiving Tysabri, talk with your doctor.

* Tysabri has a boxed warning for a certain serious side effect. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Before receiving Tysabri“ section.

How often to receive

You’ll receive one Tysabri infusion every 4 weeks.

The use of Tysabri for multiple sclerosis (MS)* may cause side effects that are mild or serious. The lists below include some of the main side effects that have been reported with Tysabri. For information about other potential side effects of the drug, talk with your doctor or pharmacist. You can also see our Tysabri side effect article or refer to the drug’s prescribing information.

Note: After the Food and Drug Administration (FDA) approves a medication, it tracks and reviews side effects of the drug. If you develop a side effect while taking Tysabri and would like to inform the FDA, visit MedWatch.

* Tysabri is also approved to treat other conditions. It’s important to note that side effects from Tysabri may differ depending on the condition it’s being used to treat.

Mild side effects

Mild side effects that can occur with Tysabri include:

These side effects of Tysabri may be temporary, lasting a few days to weeks. But if they last longer than this, or if they bother you or become severe, it’s important to talk with your doctor or pharmacist.

Serious side effects

Below are serious side effects that can occur with Tysabri:

Call your doctor right away if you develop serious side effects while using Tysabri. If the side effects seem life threatening or you think you’re having a medical emergency, call 911 or your local emergency number immediately.

* Tysabri has a boxed warning for this side effect. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Before receiving Tysabri“ section.

Allergic reaction

For some people, Tysabri can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Tysabri, your doctor may recommend a different medication instead.

Before you receive Tysabri, there’s some important information to keep in mind. The drug may not be a safe option if you have certain medical conditions or other factors that affect your health. Some of these are mentioned below.

Boxed warning: Progressive multifocal leukoencephalopathy (PML)

Tysabri has a boxed warning about an increased risk of PML. This is the most serious warning from the Food and Drug Administration (FDA).

PML is a rare but serious brain infection that may be fatal in some cases. Symptoms of PML may include:

  • confusion
  • weakness on one side of the body
  • changes in vision, memory, or personality
  • difficulty speaking

Due to this risk, Tysabri is only given in a facility certified by the Tysabri Outreach: Unified Commitment to Health (TOUCH) program. The FDA requires the TOUCH program to help make sure Tysabri is prescribed safely. After your first several doses of Tysabri, you’ll likely stay in the facility where you received the drug for at least 1 hour. This allows your doctor to monitor you closely for symptoms of PML.

If you have symptoms of PML after receiving Tysabri infusions, tell your doctor right away. They’ll likely pause your Tysabri treatment and manage your symptoms. Your doctor will advise you on whether it’s safe to continue treatment with Tysabri.

Other warnings

In addition to boxed warnings, Tysabri has other warnings.

If any of the following medical conditions or other health factors are relevant to you, talk with your doctor before receiving Tysabri:

  • if you have an infection
  • if you have a condition that affects your immune system, such as cancer or HIV
  • if you’re pregnant or breastfeeding
  • if you’ve had an allergic reaction to Tysabri drug or any of its ingredients

Read on for answers to some frequently asked questions about Tysabri for multiple sclerosis (MS).

How does Tysabri compare with Ocrevus for treating MS?

Clinical trials of Tysabri and Ocrevus have shown that both drugs are effective for treating MS. The American Academy of Neurology includes both drugs in its guidelines for treating MS. In addition, reviews of studies published in 2022, 2023, and 2024Trusted Source found both drugs to be effective for this use.

Tysabri and Ocrevus are approved to treat certain types of MS, including:

Ocrevus is also approved to treat primary progressive MS, while Tysabri is not approved for this use.

Your doctor can tell you more about whether Tysabri or Ocrevus is the right treatment option for you. You can also refer to this article for a comprehensive look at Tysabri. To learn more about Ocrevus, see this article.

How long can you stay on Tysabri for MS?

Tysabri may be used as a long-term treatment for MS. In fact, one study of Tysabri’s use for up to 15 years has shown that the drug is safe and effective for long-term use.

If you have questions about how long you’ll receive Tysabri for MS, talk with your doctor. They’ll recommend the length of treatment that’s right for your condition.

How much Tysabri costs is based on several factors. These can include your prescribed treatment regimen, your insurance plan, and your location. The price is also based on the cost of the appointment to receive doses of Tysabri from a healthcare professional

Tysabri is a brand-name drug. It’s a biologic and is not available in a biosimilar version. Brand-name biologics usually cost more than biosimilars.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.